diff --git a/plugins/inputs/tail/multiline.go b/plugins/inputs/tail/multiline.go
index 7ea2e460b..c8d5d4f6d 100644
--- a/plugins/inputs/tail/multiline.go
+++ b/plugins/inputs/tail/multiline.go
@@ -122,14 +122,14 @@ func (w *MultilineMatchWhichLine) UnmarshalText(data []byte) (err error) {
 	switch strings.ToUpper(s) {
 	case `PREVIOUS`, `"PREVIOUS"`, `'PREVIOUS'`:
 		*w = Previous
-		return
+		return nil
 
 	case `NEXT`, `"NEXT"`, `'NEXT'`:
 		*w = Next
-		return
+		return nil
 	}
 	*w = -1
-	return fmt.Errorf("E! [inputs.tail] unknown multiline MatchWhichLine")
+	return fmt.Errorf("unknown multiline MatchWhichLine")
 }
 
 // MarshalText implements encoding.TextMarshaler
@@ -138,5 +138,5 @@ func (w MultilineMatchWhichLine) MarshalText() ([]byte, error) {
 	if s != "" {
 		return []byte(s), nil
 	}
-	return nil, fmt.Errorf("E! [inputs.tail] unknown multiline MatchWhichLine")
+	return nil, fmt.Errorf("unknown multiline MatchWhichLine")
 }
diff --git a/plugins/inputs/tail/multiline_test.go b/plugins/inputs/tail/multiline_test.go
index 26a7e8029..70111f238 100644
--- a/plugins/inputs/tail/multiline_test.go
+++ b/plugins/inputs/tail/multiline_test.go
@@ -5,8 +5,9 @@ import (
 	"testing"
 	"time"
 
+	"github.com/stretchr/testify/require"
+
 	"github.com/influxdata/telegraf/config"
-	"github.com/stretchr/testify/assert"
 )
 
 func TestMultilineConfigOK(t *testing.T) {
@@ -17,7 +18,7 @@ func TestMultilineConfigOK(t *testing.T) {
 
 	_, err := c.NewMultiline()
 
-	assert.NoError(t, err, "Configuration was OK.")
+	require.NoError(t, err, "Configuration was OK.")
 }
 
 func TestMultilineConfigError(t *testing.T) {
@@ -28,7 +29,7 @@ func TestMultilineConfigError(t *testing.T) {
 
 	_, err := c.NewMultiline()
 
-	assert.Error(t, err, "The pattern was invalid")
+	require.Error(t, err, "The pattern was invalid")
 }
 
 func TestMultilineConfigTimeoutSpecified(t *testing.T) {
@@ -39,9 +40,9 @@ func TestMultilineConfigTimeoutSpecified(t *testing.T) {
 		Timeout:        &duration,
 	}
 	m, err := c.NewMultiline()
-	assert.NoError(t, err, "Configuration was OK.")
+	require.NoError(t, err, "Configuration was OK.")
 
-	assert.Equal(t, duration, *m.config.Timeout)
+	require.Equal(t, duration, *m.config.Timeout)
 }
 
 func TestMultilineConfigDefaultTimeout(t *testing.T) {
@@ -51,9 +52,9 @@ func TestMultilineConfigDefaultTimeout(t *testing.T) {
 		MatchWhichLine: Previous,
 	}
 	m, err := c.NewMultiline()
-	assert.NoError(t, err, "Configuration was OK.")
+	require.NoError(t, err, "Configuration was OK.")
 
-	assert.Equal(t, duration, *m.config.Timeout)
+	require.Equal(t, duration, *m.config.Timeout)
 }
 
 func TestMultilineIsEnabled(t *testing.T) {
@@ -62,11 +63,11 @@ func TestMultilineIsEnabled(t *testing.T) {
 		MatchWhichLine: Previous,
 	}
 	m, err := c.NewMultiline()
-	assert.NoError(t, err, "Configuration was OK.")
+	require.NoError(t, err, "Configuration was OK.")
 
 	isEnabled := m.IsEnabled()
 
-	assert.True(t, isEnabled, "Should have been enabled")
+	require.True(t, isEnabled, "Should have been enabled")
 }
 
 func TestMultilineIsDisabled(t *testing.T) {
@@ -74,11 +75,11 @@ func TestMultilineIsDisabled(t *testing.T) {
 		MatchWhichLine: Previous,
 	}
 	m, err := c.NewMultiline()
-	assert.NoError(t, err, "Configuration was OK.")
+	require.NoError(t, err, "Configuration was OK.")
 
 	isEnabled := m.IsEnabled()
 
-	assert.False(t, isEnabled, "Should have been disabled")
+	require.False(t, isEnabled, "Should have been disabled")
 }
 
 func TestMultilineFlushEmpty(t *testing.T) {
@@ -87,12 +88,12 @@ func TestMultilineFlushEmpty(t *testing.T) {
 		MatchWhichLine: Previous,
 	}
 	m, err := c.NewMultiline()
-	assert.NoError(t, err, "Configuration was OK.")
+	require.NoError(t, err, "Configuration was OK.")
 	var buffer bytes.Buffer
 
 	text := m.Flush(&buffer)
 
-	assert.Empty(t, text)
+	require.Empty(t, text)
 }
 
 func TestMultilineFlush(t *testing.T) {
@@ -101,15 +102,15 @@ func TestMultilineFlush(t *testing.T) {
 		MatchWhichLine: Previous,
 	}
 	m, err := c.NewMultiline()
-	assert.NoError(t, err, "Configuration was OK.")
+	require.NoError(t, err, "Configuration was OK.")
 	var buffer bytes.Buffer
 	_, err = buffer.WriteString("foo")
-	assert.NoError(t, err)
+	require.NoError(t, err)
 
 	text := m.Flush(&buffer)
 
-	assert.Equal(t, "foo", text)
-	assert.Zero(t, buffer.Len())
+	require.Equal(t, "foo", text)
+	require.Zero(t, buffer.Len())
 }
 
 func TestMultiLineProcessLinePrevious(t *testing.T) {
@@ -118,28 +119,28 @@ func TestMultiLineProcessLinePrevious(t *testing.T) {
 		MatchWhichLine: Previous,
 	}
 	m, err := c.NewMultiline()
-	assert.NoError(t, err, "Configuration was OK.")
+	require.NoError(t, err, "Configuration was OK.")
 	var buffer bytes.Buffer
 
 	text := m.ProcessLine("1", &buffer)
-	assert.Empty(t, text)
-	assert.NotZero(t, buffer.Len())
+	require.Empty(t, text)
+	require.NotZero(t, buffer.Len())
 
 	text = m.ProcessLine("=>2", &buffer)
-	assert.Empty(t, text)
-	assert.NotZero(t, buffer.Len())
+	require.Empty(t, text)
+	require.NotZero(t, buffer.Len())
 
 	text = m.ProcessLine("=>3", &buffer)
-	assert.Empty(t, text)
-	assert.NotZero(t, buffer.Len())
+	require.Empty(t, text)
+	require.NotZero(t, buffer.Len())
 
 	text = m.ProcessLine("4", &buffer)
-	assert.Equal(t, "1=>2=>3", text)
-	assert.NotZero(t, buffer.Len())
+	require.Equal(t, "1=>2=>3", text)
+	require.NotZero(t, buffer.Len())
 
 	text = m.ProcessLine("5", &buffer)
-	assert.Equal(t, "4", text)
-	assert.Equal(t, "5", buffer.String())
+	require.Equal(t, "4", text)
+	require.Equal(t, "5", buffer.String())
 }
 
 func TestMultiLineProcessLineNext(t *testing.T) {
@@ -148,28 +149,28 @@ func TestMultiLineProcessLineNext(t *testing.T) {
 		MatchWhichLine: Next,
 	}
 	m, err := c.NewMultiline()
-	assert.NoError(t, err, "Configuration was OK.")
+	require.NoError(t, err, "Configuration was OK.")
 	var buffer bytes.Buffer
 
 	text := m.ProcessLine("1=>", &buffer)
-	assert.Empty(t, text)
-	assert.NotZero(t, buffer.Len())
+	require.Empty(t, text)
+	require.NotZero(t, buffer.Len())
 
 	text = m.ProcessLine("2=>", &buffer)
-	assert.Empty(t, text)
-	assert.NotZero(t, buffer.Len())
+	require.Empty(t, text)
+	require.NotZero(t, buffer.Len())
 
 	text = m.ProcessLine("3=>", &buffer)
-	assert.Empty(t, text)
-	assert.NotZero(t, buffer.Len())
+	require.Empty(t, text)
+	require.NotZero(t, buffer.Len())
 
 	text = m.ProcessLine("4", &buffer)
-	assert.Equal(t, "1=>2=>3=>4", text)
-	assert.Zero(t, buffer.Len())
+	require.Equal(t, "1=>2=>3=>4", text)
+	require.Zero(t, buffer.Len())
 
 	text = m.ProcessLine("5", &buffer)
-	assert.Equal(t, "5", text)
-	assert.Zero(t, buffer.Len())
+	require.Equal(t, "5", text)
+	require.Zero(t, buffer.Len())
 }
 
 func TestMultiLineMatchStringWithInvertMatchFalse(t *testing.T) {
@@ -179,13 +180,13 @@ func TestMultiLineMatchStringWithInvertMatchFalse(t *testing.T) {
 		InvertMatch:    false,
 	}
 	m, err := c.NewMultiline()
-	assert.NoError(t, err, "Configuration was OK.")
+	require.NoError(t, err, "Configuration was OK.")
 
 	matches1 := m.matchString("t=>")
 	matches2 := m.matchString("t")
 
-	assert.True(t, matches1)
-	assert.False(t, matches2)
+	require.True(t, matches1)
+	require.False(t, matches2)
 }
 
 func TestMultiLineMatchStringWithInvertTrue(t *testing.T) {
@@ -195,41 +196,41 @@ func TestMultiLineMatchStringWithInvertTrue(t *testing.T) {
 		InvertMatch:    true,
 	}
 	m, err := c.NewMultiline()
-	assert.NoError(t, err, "Configuration was OK.")
+	require.NoError(t, err, "Configuration was OK.")
 
 	matches1 := m.matchString("t=>")
 	matches2 := m.matchString("t")
 
-	assert.False(t, matches1)
-	assert.True(t, matches2)
+	require.False(t, matches1)
+	require.True(t, matches2)
 }
 
 func TestMultilineWhat(t *testing.T) {
 	var w1 MultilineMatchWhichLine
-	assert.NoError(t, w1.UnmarshalTOML([]byte(`"previous"`)))
-	assert.Equal(t, Previous, w1)
+	require.NoError(t, w1.UnmarshalTOML([]byte(`"previous"`)))
+	require.Equal(t, Previous, w1)
 
 	var w2 MultilineMatchWhichLine
-	assert.NoError(t, w2.UnmarshalTOML([]byte(`previous`)))
-	assert.Equal(t, Previous, w2)
+	require.NoError(t, w2.UnmarshalTOML([]byte(`previous`)))
+	require.Equal(t, Previous, w2)
 
 	var w3 MultilineMatchWhichLine
-	assert.NoError(t, w3.UnmarshalTOML([]byte(`'previous'`)))
-	assert.Equal(t, Previous, w3)
+	require.NoError(t, w3.UnmarshalTOML([]byte(`'previous'`)))
+	require.Equal(t, Previous, w3)
 
 	var w4 MultilineMatchWhichLine
-	assert.NoError(t, w4.UnmarshalTOML([]byte(`"next"`)))
-	assert.Equal(t, Next, w4)
+	require.NoError(t, w4.UnmarshalTOML([]byte(`"next"`)))
+	require.Equal(t, Next, w4)
 
 	var w5 MultilineMatchWhichLine
-	assert.NoError(t, w5.UnmarshalTOML([]byte(`next`)))
-	assert.Equal(t, Next, w5)
+	require.NoError(t, w5.UnmarshalTOML([]byte(`next`)))
+	require.Equal(t, Next, w5)
 
 	var w6 MultilineMatchWhichLine
-	assert.NoError(t, w6.UnmarshalTOML([]byte(`'next'`)))
-	assert.Equal(t, Next, w6)
+	require.NoError(t, w6.UnmarshalTOML([]byte(`'next'`)))
+	require.Equal(t, Next, w6)
 
 	var w7 MultilineMatchWhichLine
-	assert.Error(t, w7.UnmarshalTOML([]byte(`nope`)))
-	assert.Equal(t, MultilineMatchWhichLine(-1), w7)
+	require.Error(t, w7.UnmarshalTOML([]byte(`nope`)))
+	require.Equal(t, MultilineMatchWhichLine(-1), w7)
 }
diff --git a/plugins/inputs/tail/tail_test.go b/plugins/inputs/tail/tail_test.go
index 908ce1087..a6ff6a7eb 100644
--- a/plugins/inputs/tail/tail_test.go
+++ b/plugins/inputs/tail/tail_test.go
@@ -9,7 +9,6 @@ import (
 	"testing"
 	"time"
 
-	"github.com/stretchr/testify/assert"
 	"github.com/stretchr/testify/require"
 
 	"github.com/influxdata/telegraf"
@@ -81,7 +80,7 @@ func TestTailBadLine(t *testing.T) {
 	acc.Wait(1)
 
 	tt.Stop()
-	assert.Contains(t, buf.String(), "Malformed log line")
+	require.Contains(t, buf.String(), "Malformed log line")
 }
 
 func TestTailDosLineEndings(t *testing.T) {
@@ -137,7 +136,7 @@ func TestGrokParseLogFilesWithMultiline(t *testing.T) {
 	require.NoError(t, err)
 
 	acc := testutil.Accumulator{}
-	assert.NoError(t, tt.Start(&acc))
+	require.NoError(t, tt.Start(&acc))
 	defer tt.Stop()
 
 	acc.Wait(3)
@@ -168,7 +167,7 @@ func TestGrokParseLogFilesWithMultiline(t *testing.T) {
 			"loglevel": "ERROR",
 		})
 
-	assert.Equal(t, uint64(3), acc.NMetrics())
+	require.Equal(t, uint64(3), acc.NMetrics())
 }
 
 func TestGrokParseLogFilesWithMultilineTimeout(t *testing.T) {
@@ -201,7 +200,7 @@ func TestGrokParseLogFilesWithMultilineTimeout(t *testing.T) {
 	require.NoError(t, err)
 
 	acc := testutil.Accumulator{}
-	assert.NoError(t, tt.Start(&acc))
+	require.NoError(t, tt.Start(&acc))
 	time.Sleep(11 * time.Millisecond) // will force timeout
 	_, err = tmpfile.WriteString("[04/Jun/2016:12:41:48 +0100] INFO HelloExample: This is info\r\n")
 	require.NoError(t, err)
@@ -213,7 +212,7 @@ func TestGrokParseLogFilesWithMultilineTimeout(t *testing.T) {
 	require.NoError(t, tmpfile.Sync())
 	acc.Wait(3)
 	tt.Stop()
-	assert.Equal(t, uint64(3), acc.NMetrics())
+	require.Equal(t, uint64(3), acc.NMetrics())
 	expectedPath := tmpfile.Name()
 
 	acc.AssertContainsTaggedFields(t, "tail_grok",
@@ -254,9 +253,9 @@ func TestGrokParseLogFilesWithMultilineTailerCloseFlushesMultilineBuffer(t *test
 	require.NoError(t, err)
 
 	acc := testutil.Accumulator{}
-	assert.NoError(t, tt.Start(&acc))
+	require.NoError(t, tt.Start(&acc))
 	acc.Wait(3)
-	assert.Equal(t, uint64(3), acc.NMetrics())
+	require.Equal(t, uint64(3), acc.NMetrics())
 	// Close tailer, so multiline buffer is flushed
 	tt.Stop()
 	acc.Wait(4)
@@ -561,7 +560,6 @@ func TestCharacterEncoding(t *testing.T) {
 	}
 	for _, tt := range tests {
 		t.Run(tt.name, func(t *testing.T) {
-
 			plugin := &Tail{
 				Files:               []string{filepath.Join(testdataDir, tt.testfiles)},
 				FromBeginning:       tt.fromBeginning,
diff --git a/plugins/inputs/tcp_listener/tcp_listener.go b/plugins/inputs/tcp_listener/tcp_listener.go
index aedaa7276..8eeaa9cff 100644
--- a/plugins/inputs/tcp_listener/tcp_listener.go
+++ b/plugins/inputs/tcp_listener/tcp_listener.go
@@ -3,7 +3,6 @@ package tcp_listener
 import (
 	"bufio"
 	"fmt"
-	"log"
 	"net"
 	"sync"
 
@@ -88,7 +87,7 @@ func (t *TCPListener) Start(acc telegraf.Accumulator) error {
 	t.Lock()
 	defer t.Unlock()
 
-	log.Println("W! DEPRECATED: the TCP listener plugin has been deprecated " +
+	t.Log.Warn("DEPRECATED: the TCP listener plugin has been deprecated " +
 		"in favor of the socket_listener plugin " +
 		"(https://github.com/influxdata/telegraf/tree/master/plugins/inputs/socket_listener)")
 
diff --git a/plugins/inputs/tcp_listener/tcp_listener_test.go b/plugins/inputs/tcp_listener/tcp_listener_test.go
index 9203318af..e59115e67 100644
--- a/plugins/inputs/tcp_listener/tcp_listener_test.go
+++ b/plugins/inputs/tcp_listener/tcp_listener_test.go
@@ -11,11 +11,10 @@ import (
 	"strings"
 	"testing"
 
+	"github.com/stretchr/testify/require"
+
 	"github.com/influxdata/telegraf/plugins/parsers"
 	"github.com/influxdata/telegraf/testutil"
-
-	"github.com/stretchr/testify/assert"
-	"github.com/stretchr/testify/require"
 )
 
 const (
@@ -96,10 +95,10 @@ func TestHighTrafficTCP(t *testing.T) {
 	require.NoError(t, conn.(*net.TCPConn).CloseWrite())
 	buf := []byte{0}
 	_, err = conn.Read(buf)
-	assert.Equal(t, err, io.EOF)
+	require.Equal(t, err, io.EOF)
 	listener.Stop()
 
-	assert.Equal(t, 100000, int(acc.NMetrics()))
+	require.Equal(t, 100000, int(acc.NMetrics()))
 }
 
 func TestConnectTCP(t *testing.T) {
@@ -168,14 +167,14 @@ func TestConcurrentConns(t *testing.T) {
 	buf := make([]byte, 1500)
 	n, err := conn.Read(buf)
 	require.NoError(t, err)
-	assert.Equal(t,
+	require.Equal(t,
 		"Telegraf maximum concurrent TCP connections (2) reached, closing.\n"+
 			"You may want to increase max_tcp_connections in"+
 			" the Telegraf tcp listener configuration.\n",
 		string(buf[:n]))
 
 	_, err = conn.Read(buf)
-	assert.Equal(t, io.EOF, err)
+	require.Equal(t, io.EOF, err)
 }
 
 // Test that MaxTCPConnections is respected when max==1
@@ -203,14 +202,14 @@ func TestConcurrentConns1(t *testing.T) {
 	buf := make([]byte, 1500)
 	n, err := conn.Read(buf)
 	require.NoError(t, err)
-	assert.Equal(t,
+	require.Equal(t,
 		"Telegraf maximum concurrent TCP connections (1) reached, closing.\n"+
 			"You may want to increase max_tcp_connections in"+
 			" the Telegraf tcp listener configuration.\n",
 		string(buf[:n]))
 
 	_, err = conn.Read(buf)
-	assert.Equal(t, io.EOF, err)
+	require.Equal(t, io.EOF, err)
 }
 
 // Test that MaxTCPConnections is respected
diff --git a/plugins/inputs/tengine/tengine_test.go b/plugins/inputs/tengine/tengine_test.go
index d91c97465..595b8e3ba 100644
--- a/plugins/inputs/tengine/tengine_test.go
+++ b/plugins/inputs/tengine/tengine_test.go
@@ -8,9 +8,9 @@ import (
 	"net/url"
 	"testing"
 
-	"github.com/influxdata/telegraf/testutil"
-	"github.com/stretchr/testify/assert"
 	"github.com/stretchr/testify/require"
+
+	"github.com/influxdata/telegraf/testutil"
 )
 
 const tengineSampleResponse = `127.0.0.1,784,1511,2,2,1,0,1,0,0,0,0,0,0,1,0,0,0,0,1,0,0,0,0,0,0,0,0,0,0`
@@ -22,7 +22,7 @@ func TestTengineTags(t *testing.T) {
 	for _, url1 := range urls {
 		addr, _ = url.Parse(url1)
 		tagMap := getTags(addr, "127.0.0.1")
-		assert.Contains(t, tagMap["server"], "localhost")
+		require.Contains(t, tagMap["server"], "localhost")
 	}
 }
 
diff --git a/plugins/inputs/twemproxy/twemproxy.go b/plugins/inputs/twemproxy/twemproxy.go
index b4c4b52f8..c629c37ff 100644
--- a/plugins/inputs/twemproxy/twemproxy.go
+++ b/plugins/inputs/twemproxy/twemproxy.go
@@ -44,7 +44,7 @@ func (t *Twemproxy) Gather(acc telegraf.Accumulator) error {
 
 	var stats map[string]interface{}
 	if err = json.Unmarshal(body, &stats); err != nil {
-		return errors.New("Error decoding JSON response")
+		return errors.New("error decoding JSON response")
 	}
 
 	tags := make(map[string]string)
@@ -124,11 +124,8 @@ func (t *Twemproxy) processServer(
 ) {
 	fields := make(map[string]interface{})
 	for key, value := range data {
-		switch key {
-		default:
-			if val, ok := value.(float64); ok {
-				fields[key] = val
-			}
+		if val, ok := value.(float64); ok {
+			fields[key] = val
 		}
 	}
 	acc.AddFields("twemproxy_pool_server", fields, tags)
diff --git a/plugins/inputs/twemproxy/twemproxy_test.go b/plugins/inputs/twemproxy/twemproxy_test.go
index 0da1694d5..8d5c5eef1 100644
--- a/plugins/inputs/twemproxy/twemproxy_test.go
+++ b/plugins/inputs/twemproxy/twemproxy_test.go
@@ -5,8 +5,9 @@ import (
 	"net"
 	"testing"
 
-	"github.com/influxdata/telegraf/testutil"
 	"github.com/stretchr/testify/require"
+
+	"github.com/influxdata/telegraf/testutil"
 )
 
 const sampleAddr = "127.0.0.1:22222"
@@ -65,15 +66,12 @@ func mockTwemproxyServer() (net.Listener, error) {
 		return nil, err
 	}
 	go func(l net.Listener) {
-		for {
-			conn, _ := l.Accept()
-			if _, err := conn.Write([]byte(sampleStats)); err != nil {
-				return
-			}
-			if err := conn.Close(); err != nil {
-				return
-			}
-			break
+		conn, _ := l.Accept()
+		if _, err := conn.Write([]byte(sampleStats)); err != nil {
+			return
+		}
+		if err := conn.Close(); err != nil {
+			return
 		}
 	}(listener)
 
diff --git a/plugins/inputs/udp_listener/udp_listener.go b/plugins/inputs/udp_listener/udp_listener.go
index 07cd79cb2..39fef79ce 100644
--- a/plugins/inputs/udp_listener/udp_listener.go
+++ b/plugins/inputs/udp_listener/udp_listener.go
@@ -2,7 +2,6 @@ package udp_listener
 
 import (
 	"fmt"
-	"log"
 	"net"
 	"sync"
 	"time"
@@ -96,7 +95,7 @@ func (u *UDPListener) Start(acc telegraf.Accumulator) error {
 	u.Lock()
 	defer u.Unlock()
 
-	log.Println("W! DEPRECATED: the UDP listener plugin has been deprecated " +
+	u.Log.Warn("DEPRECATED: the UDP listener plugin has been deprecated " +
 		"in favor of the socket_listener plugin " +
 		"(https://github.com/influxdata/telegraf/tree/master/plugins/inputs/socket_listener)")
 
@@ -172,8 +171,7 @@ func (u *UDPListener) udpListenLoop() {
 
 			n, _, err := u.listener.ReadFromUDP(buf)
 			if err != nil {
-				if err, ok := err.(net.Error); ok && err.Timeout() {
-				} else {
+				if err, ok := err.(net.Error); !ok || !err.Timeout() {
 					u.Log.Error(err.Error())
 				}
 				continue
diff --git a/plugins/inputs/unbound/unbound_test.go b/plugins/inputs/unbound/unbound_test.go
index d39006024..e9994d7eb 100644
--- a/plugins/inputs/unbound/unbound_test.go
+++ b/plugins/inputs/unbound/unbound_test.go
@@ -4,8 +4,9 @@ import (
 	"bytes"
 	"testing"
 
+	"github.com/stretchr/testify/require"
+
 	"github.com/influxdata/telegraf/testutil"
-	"github.com/stretchr/testify/assert"
 )
 
 func UnboundControl(output string) func(unbound Unbound) (*bytes.Buffer, error) {
@@ -21,12 +22,12 @@ func TestParseFullOutput(t *testing.T) {
 	}
 	err := v.Gather(acc)
 
-	assert.NoError(t, err)
+	require.NoError(t, err)
 
-	assert.True(t, acc.HasMeasurement("unbound"))
+	require.True(t, acc.HasMeasurement("unbound"))
 
-	assert.Len(t, acc.Metrics, 1)
-	assert.Equal(t, acc.NFields(), 63)
+	require.Len(t, acc.Metrics, 1)
+	require.Equal(t, acc.NFields(), 63)
 
 	acc.AssertContainsFields(t, "unbound", parsedFullOutput)
 }
@@ -39,13 +40,13 @@ func TestParseFullOutputThreadAsTag(t *testing.T) {
 	}
 	err := v.Gather(acc)
 
-	assert.NoError(t, err)
+	require.NoError(t, err)
 
-	assert.True(t, acc.HasMeasurement("unbound"))
-	assert.True(t, acc.HasMeasurement("unbound_threads"))
+	require.True(t, acc.HasMeasurement("unbound"))
+	require.True(t, acc.HasMeasurement("unbound_threads"))
 
-	assert.Len(t, acc.Metrics, 2)
-	assert.Equal(t, acc.NFields(), 63)
+	require.Len(t, acc.Metrics, 2)
+	require.Equal(t, acc.NFields(), 63)
 
 	acc.AssertContainsFields(t, "unbound", parsedFullOutputThreadAsTagMeasurementUnbound)
 	acc.AssertContainsFields(t, "unbound_threads", parsedFullOutputThreadAsTagMeasurementUnboundThreads)
diff --git a/plugins/inputs/uwsgi/uwsgi.go b/plugins/inputs/uwsgi/uwsgi.go
index f536e4b27..9e260a5fe 100644
--- a/plugins/inputs/uwsgi/uwsgi.go
+++ b/plugins/inputs/uwsgi/uwsgi.go
@@ -78,20 +78,20 @@ func (u *Uwsgi) Gather(acc telegraf.Accumulator) error {
 	return nil
 }
 
-func (u *Uwsgi) gatherServer(acc telegraf.Accumulator, url *url.URL) error {
+func (u *Uwsgi) gatherServer(acc telegraf.Accumulator, address *url.URL) error {
 	var err error
 	var r io.ReadCloser
 	var s StatsServer
 
-	switch url.Scheme {
+	switch address.Scheme {
 	case "tcp":
-		r, err = net.DialTimeout(url.Scheme, url.Host, time.Duration(u.Timeout))
+		r, err = net.DialTimeout(address.Scheme, address.Host, time.Duration(u.Timeout))
 		if err != nil {
 			return err
 		}
-		s.source = url.Host
+		s.source = address.Host
 	case "unix":
-		r, err = net.DialTimeout(url.Scheme, url.Path, time.Duration(u.Timeout))
+		r, err = net.DialTimeout(address.Scheme, address.Path, time.Duration(u.Timeout))
 		if err != nil {
 			return err
 		}
@@ -100,20 +100,20 @@ func (u *Uwsgi) gatherServer(acc telegraf.Accumulator, url *url.URL) error {
 			s.source = ""
 		}
 	case "http":
-		resp, err := u.client.Get(url.String())
+		resp, err := u.client.Get(address.String()) //nolint:bodyclose // response body is closed after switch
 		if err != nil {
 			return err
 		}
 		r = resp.Body
-		s.source = url.Host
+		s.source = address.Host
 	default:
-		return fmt.Errorf("'%s' is not a supported scheme", url.Scheme)
+		return fmt.Errorf("'%s' is not a supported scheme", address.Scheme)
 	}
 
 	defer r.Close()
 
 	if err := json.NewDecoder(r).Decode(&s); err != nil {
-		return fmt.Errorf("failed to decode json payload from '%s': %s", url.String(), err.Error())
+		return fmt.Errorf("failed to decode json payload from '%s': %s", address.String(), err.Error())
 	}
 
 	u.gatherStatServer(acc, &s)
diff --git a/plugins/inputs/varnish/varnish_test.go b/plugins/inputs/varnish/varnish_test.go
index 088c08378..a5676e9d3 100644
--- a/plugins/inputs/varnish/varnish_test.go
+++ b/plugins/inputs/varnish/varnish_test.go
@@ -9,7 +9,7 @@ import (
 	"strings"
 	"testing"
 
-	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
 
 	"github.com/influxdata/telegraf/config"
 	"github.com/influxdata/telegraf/testutil"
@@ -27,7 +27,7 @@ func TestGather(t *testing.T) {
 		run:   fakeVarnishStat(smOutput),
 		Stats: []string{"*"},
 	}
-	assert.NoError(t, v.Gather(acc))
+	require.NoError(t, v.Gather(acc))
 
 	acc.HasMeasurement("varnish")
 	for tag, fields := range parsedSmOutput {
@@ -43,12 +43,12 @@ func TestParseFullOutput(t *testing.T) {
 		run:   fakeVarnishStat(fullOutput),
 		Stats: []string{"*"},
 	}
-	assert.NoError(t, v.Gather(acc))
+	require.NoError(t, v.Gather(acc))
 
 	acc.HasMeasurement("varnish")
 	flat := flatten(acc.Metrics)
-	assert.Len(t, acc.Metrics, 6)
-	assert.Equal(t, 293, len(flat))
+	require.Len(t, acc.Metrics, 6)
+	require.Equal(t, 293, len(flat))
 }
 
 func TestFilterSomeStats(t *testing.T) {
@@ -57,12 +57,12 @@ func TestFilterSomeStats(t *testing.T) {
 		run:   fakeVarnishStat(fullOutput),
 		Stats: []string{"MGT.*", "VBE.*"},
 	}
-	assert.NoError(t, v.Gather(acc))
+	require.NoError(t, v.Gather(acc))
 
 	acc.HasMeasurement("varnish")
 	flat := flatten(acc.Metrics)
-	assert.Len(t, acc.Metrics, 2)
-	assert.Equal(t, 16, len(flat))
+	require.Len(t, acc.Metrics, 2)
+	require.Equal(t, 16, len(flat))
 }
 
 func TestFieldConfig(t *testing.T) {
@@ -79,11 +79,11 @@ func TestFieldConfig(t *testing.T) {
 			run:   fakeVarnishStat(fullOutput),
 			Stats: strings.Split(fieldCfg, ","),
 		}
-		assert.NoError(t, v.Gather(acc))
+		require.NoError(t, v.Gather(acc))
 
 		acc.HasMeasurement("varnish")
 		flat := flatten(acc.Metrics)
-		assert.Equal(t, expected, len(flat))
+		require.Equal(t, expected, len(flat))
 	}
 }
 
diff --git a/plugins/inputs/vsphere/endpoint.go b/plugins/inputs/vsphere/endpoint.go
index 9903647f8..b0aab7dfd 100644
--- a/plugins/inputs/vsphere/endpoint.go
+++ b/plugins/inputs/vsphere/endpoint.go
@@ -14,20 +14,20 @@ import (
 	"sync/atomic"
 	"time"
 
-	"github.com/influxdata/telegraf/filter"
-
 	"github.com/influxdata/telegraf"
 	"github.com/vmware/govmomi/object"
 	"github.com/vmware/govmomi/performance"
 	"github.com/vmware/govmomi/vim25/mo"
 	"github.com/vmware/govmomi/vim25/types"
+
+	"github.com/influxdata/telegraf/filter"
 )
 
-var isolateLUN = regexp.MustCompile(".*/([^/]+)/?$")
+var isolateLUN = regexp.MustCompile(`.*/([^/]+)/?$`)
 
-var isIPv4 = regexp.MustCompile("^(?:[0-9]{1,3}\\.){3}[0-9]{1,3}$")
+var isIPv4 = regexp.MustCompile(`^(?:[0-9]{1,3}\.){3}[0-9]{1,3}$`)
 
-var isIPv6 = regexp.MustCompile("^(?:[A-Fa-f0-9]{0,4}:){1,7}[A-Fa-f0-9]{1,4}$")
+var isIPv6 = regexp.MustCompile(`^(?:[A-Fa-f0-9]{0,4}:){1,7}[A-Fa-f0-9]{1,4}$`)
 
 const maxSampleConst = 10 // Absolute maximum number of samples regardless of period
 
@@ -115,14 +115,14 @@ func (e *Endpoint) getParent(obj *objectRef, res *resourceKind) (*objectRef, boo
 
 // NewEndpoint returns a new connection to a vCenter based on the URL and configuration passed
 // as parameters.
-func NewEndpoint(ctx context.Context, parent *VSphere, url *url.URL, log telegraf.Logger) (*Endpoint, error) {
+func NewEndpoint(ctx context.Context, parent *VSphere, address *url.URL, log telegraf.Logger) (*Endpoint, error) {
 	e := Endpoint{
-		URL:               url,
+		URL:               address,
 		Parent:            parent,
-		hwMarks:           NewTSCache(hwMarkTTL),
+		hwMarks:           NewTSCache(hwMarkTTL, log),
 		lun2ds:            make(map[string]string),
 		initialized:       false,
-		clientFactory:     NewClientFactory(url, parent),
+		clientFactory:     NewClientFactory(address, parent),
 		customAttrFilter:  newFilterOrPanic(parent.CustomAttributeInclude, parent.CustomAttributeExclude),
 		customAttrEnabled: anythingEnabled(parent.CustomAttributeExclude),
 		log:               log,
@@ -457,9 +457,6 @@ func (e *Endpoint) discover(ctx context.Context) error {
 			SendInternalCounterWithTags("discovered_objects", e.URL.Host, map[string]string{"type": res.name}, int64(len(objects)))
 			numRes += int64(len(objects))
 		}
-		if err != nil {
-			e.log.Error(err)
-		}
 	}
 
 	// Build lun2ds map
@@ -584,11 +581,11 @@ func (e *Endpoint) complexMetadataSelect(ctx context.Context, res *resourceKind,
 	te.Wait()
 }
 
-func getDatacenters(ctx context.Context, e *Endpoint, filter *ResourceFilter) (objectMap, error) {
+func getDatacenters(ctx context.Context, e *Endpoint, resourceFilter *ResourceFilter) (objectMap, error) {
 	var resources []mo.Datacenter
 	ctx1, cancel1 := context.WithTimeout(ctx, time.Duration(e.Parent.Timeout))
 	defer cancel1()
-	err := filter.FindAll(ctx1, &resources)
+	err := resourceFilter.FindAll(ctx1, &resources)
 	if err != nil {
 		return nil, err
 	}
@@ -605,11 +602,11 @@ func getDatacenters(ctx context.Context, e *Endpoint, filter *ResourceFilter) (o
 	return m, nil
 }
 
-func getClusters(ctx context.Context, e *Endpoint, filter *ResourceFilter) (objectMap, error) {
+func getClusters(ctx context.Context, e *Endpoint, resourceFilter *ResourceFilter) (objectMap, error) {
 	var resources []mo.ClusterComputeResource
 	ctx1, cancel1 := context.WithTimeout(ctx, time.Duration(e.Parent.Timeout))
 	defer cancel1()
-	err := filter.FindAll(ctx1, &resources)
+	err := resourceFilter.FindAll(ctx1, &resources)
 	if err != nil {
 		return nil, err
 	}
@@ -657,9 +654,9 @@ func getClusters(ctx context.Context, e *Endpoint, filter *ResourceFilter) (obje
 }
 
 //noinspection GoUnusedParameter
-func getHosts(ctx context.Context, e *Endpoint, filter *ResourceFilter) (objectMap, error) {
+func getHosts(ctx context.Context, e *Endpoint, resourceFilter *ResourceFilter) (objectMap, error) {
 	var resources []mo.HostSystem
-	err := filter.FindAll(ctx, &resources)
+	err := resourceFilter.FindAll(ctx, &resources)
 	if err != nil {
 		return nil, err
 	}
@@ -675,11 +672,11 @@ func getHosts(ctx context.Context, e *Endpoint, filter *ResourceFilter) (objectM
 	return m, nil
 }
 
-func getVMs(ctx context.Context, e *Endpoint, filter *ResourceFilter) (objectMap, error) {
+func getVMs(ctx context.Context, e *Endpoint, resourceFilter *ResourceFilter) (objectMap, error) {
 	var resources []mo.VirtualMachine
 	ctx1, cancel1 := context.WithTimeout(ctx, time.Duration(e.Parent.Timeout))
 	defer cancel1()
-	err := filter.FindAll(ctx1, &resources)
+	err := resourceFilter.FindAll(ctx1, &resources)
 	if err != nil {
 		return nil, err
 	}
@@ -765,11 +762,11 @@ func getVMs(ctx context.Context, e *Endpoint, filter *ResourceFilter) (objectMap
 	return m, nil
 }
 
-func getDatastores(ctx context.Context, e *Endpoint, filter *ResourceFilter) (objectMap, error) {
+func getDatastores(ctx context.Context, e *Endpoint, resourceFilter *ResourceFilter) (objectMap, error) {
 	var resources []mo.Datastore
 	ctx1, cancel1 := context.WithTimeout(ctx, time.Duration(e.Parent.Timeout))
 	defer cancel1()
-	err := filter.FindAll(ctx1, &resources)
+	err := resourceFilter.FindAll(ctx1, &resources)
 	if err != nil {
 		return nil, err
 	}
@@ -888,7 +885,7 @@ func (e *Endpoint) chunkify(ctx context.Context, res *resourceKind, now time.Tim
 	pqs := make(queryChunk, 0, e.Parent.MaxQueryObjects)
 	numQs := 0
 
-	for _, object := range res.objects {
+	for _, obj := range res.objects {
 		timeBuckets := make(map[int64]*types.PerfQuerySpec)
 		for metricIdx, metric := range res.metrics {
 			// Determine time of last successful collection
@@ -897,7 +894,7 @@ func (e *Endpoint) chunkify(ctx context.Context, res *resourceKind, now time.Tim
 				e.log.Infof("Unable to find metric name for id %d. Skipping!", metric.CounterId)
 				continue
 			}
-			start, ok := e.hwMarks.Get(object.ref.Value, metricName)
+			start, ok := e.hwMarks.Get(obj.ref.Value, metricName)
 			if !ok {
 				start = latest.Add(time.Duration(-res.sampling) * time.Second * (time.Duration(e.Parent.MetricLookback) - 1))
 			}
@@ -907,7 +904,7 @@ func (e *Endpoint) chunkify(ctx context.Context, res *resourceKind, now time.Tim
 			bucket, ok := timeBuckets[start.Unix()]
 			if !ok {
 				bucket = &types.PerfQuerySpec{
-					Entity:     object.ref,
+					Entity:     obj.ref,
 					MaxSample:  maxSampleConst,
 					MetricId:   make([]types.PerfMetricId, 0),
 					IntervalId: res.sampling,
@@ -1272,7 +1269,7 @@ func (e *Endpoint) populateTags(objectRef *objectRef, resourceType string, resou
 	}
 }
 
-func (e *Endpoint) makeMetricIdentifier(prefix, metric string) (string, string) {
+func (e *Endpoint) makeMetricIdentifier(prefix, metric string) (metricName string, fieldName string) {
 	parts := strings.Split(metric, ".")
 	if len(parts) == 1 {
 		return prefix, parts[0]
diff --git a/plugins/inputs/vsphere/finder.go b/plugins/inputs/vsphere/finder.go
index 8414ad8d8..0af9ef912 100644
--- a/plugins/inputs/vsphere/finder.go
+++ b/plugins/inputs/vsphere/finder.go
@@ -35,14 +35,14 @@ type ResourceFilter struct {
 func (f *Finder) FindAll(ctx context.Context, resType string, paths, excludePaths []string, dst interface{}) error {
 	objs := make(map[string]types.ObjectContent)
 	for _, p := range paths {
-		if err := f.find(ctx, resType, p, objs); err != nil {
+		if err := f.findResources(ctx, resType, p, objs); err != nil {
 			return err
 		}
 	}
 	if len(excludePaths) > 0 {
 		excludes := make(map[string]types.ObjectContent)
 		for _, p := range excludePaths {
-			if err := f.find(ctx, resType, p, excludes); err != nil {
+			if err := f.findResources(ctx, resType, p, excludes); err != nil {
 				return err
 			}
 		}
@@ -56,14 +56,14 @@ func (f *Finder) FindAll(ctx context.Context, resType string, paths, excludePath
 // Find returns the resources matching the specified path.
 func (f *Finder) Find(ctx context.Context, resType, path string, dst interface{}) error {
 	objs := make(map[string]types.ObjectContent)
-	err := f.find(ctx, resType, path, objs)
+	err := f.findResources(ctx, resType, path, objs)
 	if err != nil {
 		return err
 	}
 	return objectContentToTypedArray(objs, dst)
 }
 
-func (f *Finder) find(ctx context.Context, resType, path string, objs map[string]types.ObjectContent) error {
+func (f *Finder) findResources(ctx context.Context, resType, path string, objs map[string]types.ObjectContent) error {
 	p := strings.Split(path, "/")
 	flt := make([]property.Filter, len(p)-1)
 	for i := 1; i < len(p); i++ {
@@ -107,7 +107,7 @@ func (f *Finder) descend(ctx context.Context, root types.ManagedObjectReference,
 	fields := []string{"name"}
 	recurse := tokens[pos]["name"] == "**"
 
-	types := ct
+	objectTypes := ct
 	if isLeaf {
 		if af, ok := addFields[resType]; ok {
 			fields = append(fields, af...)
@@ -131,9 +131,9 @@ func (f *Finder) descend(ctx context.Context, root types.ManagedObjectReference,
 			}
 			return nil
 		}
-		types = []string{resType} // Only load wanted object type at leaf level
+		objectTypes = []string{resType} // Only load wanted object type at leaf level
 	}
-	err = v.Retrieve(ctx, types, fields, &content)
+	err = v.Retrieve(ctx, objectTypes, fields, &content)
 	if err != nil {
 		return err
 	}
diff --git a/plugins/inputs/vsphere/tscache.go b/plugins/inputs/vsphere/tscache.go
index c312260c8..78303b45d 100644
--- a/plugins/inputs/vsphere/tscache.go
+++ b/plugins/inputs/vsphere/tscache.go
@@ -1,9 +1,10 @@
 package vsphere
 
 import (
-	"log"
 	"sync"
 	"time"
+
+	"github.com/influxdata/telegraf"
 )
 
 // TSCache is a cache of timestamps used to determine the validity of datapoints
@@ -11,13 +12,15 @@ type TSCache struct {
 	ttl   time.Duration
 	table map[string]time.Time
 	mux   sync.RWMutex
+	log   telegraf.Logger
 }
 
 // NewTSCache creates a new TSCache with a specified time-to-live after which timestamps are discarded.
-func NewTSCache(ttl time.Duration) *TSCache {
+func NewTSCache(ttl time.Duration, log telegraf.Logger) *TSCache {
 	return &TSCache{
 		ttl:   ttl,
 		table: make(map[string]time.Time),
+		log:   log,
 	}
 }
 
@@ -32,7 +35,7 @@ func (t *TSCache) Purge() {
 			n++
 		}
 	}
-	log.Printf("D! [inputs.vsphere] purged timestamp cache. %d deleted with %d remaining", n, len(t.table))
+	t.log.Debugf("purged timestamp cache. %d deleted with %d remaining", n, len(t.table))
 }
 
 // IsNew returns true if the supplied timestamp for the supplied key is more recent than the
@@ -56,10 +59,10 @@ func (t *TSCache) Get(key string, metricName string) (time.Time, bool) {
 }
 
 // Put updates the latest timestamp for the supplied key.
-func (t *TSCache) Put(key string, metricName string, time time.Time) {
+func (t *TSCache) Put(key string, metricName string, timestamp time.Time) {
 	t.mux.Lock()
 	defer t.mux.Unlock()
-	t.table[makeKey(key, metricName)] = time
+	t.table[makeKey(key, metricName)] = timestamp
 }
 
 func makeKey(resource string, metric string) string {
diff --git a/plugins/inputs/vsphere/vsphere_test.go b/plugins/inputs/vsphere/vsphere_test.go
index 31bb0fdf0..2e8654efc 100644
--- a/plugins/inputs/vsphere/vsphere_test.go
+++ b/plugins/inputs/vsphere/vsphere_test.go
@@ -11,15 +11,16 @@ import (
 	"time"
 	"unsafe"
 
-	"github.com/influxdata/telegraf/config"
-	itls "github.com/influxdata/telegraf/plugins/common/tls"
-	"github.com/influxdata/telegraf/testutil"
 	"github.com/influxdata/toml"
 	"github.com/stretchr/testify/require"
 	"github.com/vmware/govmomi/object"
 	"github.com/vmware/govmomi/simulator"
 	"github.com/vmware/govmomi/vim25/mo"
 	"github.com/vmware/govmomi/vim25/types"
+
+	"github.com/influxdata/telegraf/config"
+	itls "github.com/influxdata/telegraf/plugins/common/tls"
+	"github.com/influxdata/telegraf/testutil"
 )
 
 var configHeader = `
@@ -229,7 +230,6 @@ func TestParseConfig(t *testing.T) {
 	tab, err := toml.Parse([]byte(c))
 	require.NoError(t, err)
 	require.NotNil(t, tab)
-
 }
 
 func TestConfigDurationParsing(t *testing.T) {
@@ -313,6 +313,7 @@ func TestFinder(t *testing.T) {
 	ctx := context.Background()
 
 	c, err := NewClient(ctx, s.URL, v)
+	require.NoError(t, err)
 
 	f := Finder{c}
 
@@ -429,6 +430,7 @@ func TestFolders(t *testing.T) {
 	v := defaultVSphere()
 
 	c, err := NewClient(ctx, s.URL, v)
+	require.NoError(t, err)
 
 	f := Finder{c}
 
@@ -449,7 +451,7 @@ func TestFolders(t *testing.T) {
 	testLookupVM(ctx, t, &f, "/F0/DC1/vm/**/F*/**", 4, "")
 }
 
-func TestCollection(t *testing.T) {
+func TestCollectionWithClusterMetrics(t *testing.T) {
 	testCollection(t, false)
 }
 
diff --git a/plugins/inputs/win_perf_counters/win_perf_counters_integration_test.go b/plugins/inputs/win_perf_counters/win_perf_counters_integration_test.go
index a5ae58370..c7ceec815 100644
--- a/plugins/inputs/win_perf_counters/win_perf_counters_integration_test.go
+++ b/plugins/inputs/win_perf_counters/win_perf_counters_integration_test.go
@@ -6,14 +6,13 @@ package win_perf_counters
 import (
 	"errors"
 	"fmt"
+	"strings"
 	"testing"
 	"time"
 
-	"strings"
+	"github.com/stretchr/testify/require"
 
 	"github.com/influxdata/telegraf/testutil"
-	"github.com/stretchr/testify/assert"
-	"github.com/stretchr/testify/require"
 )
 
 func TestWinPerformanceQueryImplIntegration(t *testing.T) {
@@ -30,15 +29,15 @@ func TestWinPerformanceQueryImplIntegration(t *testing.T) {
 
 	_, err = query.AddCounterToQuery("")
 	require.Error(t, err, "uninitialized query must return errors")
-	assert.True(t, strings.Contains(err.Error(), "uninitialized"))
+	require.True(t, strings.Contains(err.Error(), "uninitialized"))
 
 	_, err = query.AddEnglishCounterToQuery("")
 	require.Error(t, err, "uninitialized query must return errors")
-	assert.True(t, strings.Contains(err.Error(), "uninitialized"))
+	require.True(t, strings.Contains(err.Error(), "uninitialized"))
 
 	err = query.CollectData()
 	require.Error(t, err, "uninitialized query must return errors")
-	assert.True(t, strings.Contains(err.Error(), "uninitialized"))
+	require.True(t, strings.Contains(err.Error(), "uninitialized"))
 
 	err = query.Open()
 	require.NoError(t, err)
@@ -47,7 +46,7 @@ func TestWinPerformanceQueryImplIntegration(t *testing.T) {
 
 	hCounter, err = query.AddCounterToQuery(counterPath)
 	require.NoError(t, err)
-	assert.NotEqual(t, 0, hCounter)
+	require.NotEqual(t, 0, hCounter)
 
 	err = query.Close()
 	require.NoError(t, err)
@@ -57,11 +56,11 @@ func TestWinPerformanceQueryImplIntegration(t *testing.T) {
 
 	hCounter, err = query.AddEnglishCounterToQuery(counterPath)
 	require.NoError(t, err)
-	assert.NotEqual(t, 0, hCounter)
+	require.NotEqual(t, 0, hCounter)
 
 	cp, err := query.GetCounterPath(hCounter)
 	require.NoError(t, err)
-	assert.True(t, strings.HasSuffix(cp, counterPath))
+	require.True(t, strings.HasSuffix(cp, counterPath))
 
 	err = query.CollectData()
 	require.NoError(t, err)
@@ -76,19 +75,19 @@ func TestWinPerformanceQueryImplIntegration(t *testing.T) {
 	now := time.Now()
 	mtime, err := query.CollectDataWithTime()
 	require.NoError(t, err)
-	assert.True(t, mtime.Sub(now) < time.Second)
+	require.True(t, mtime.Sub(now) < time.Second)
 
 	counterPath = "\\Process(*)\\% Processor Time"
 	paths, err := query.ExpandWildCardPath(counterPath)
 	require.NoError(t, err)
 	require.NotNil(t, paths)
-	assert.True(t, len(paths) > 1)
+	require.True(t, len(paths) > 1)
 
 	counterPath = "\\Process(_Total)\\*"
 	paths, err = query.ExpandWildCardPath(counterPath)
 	require.NoError(t, err)
 	require.NotNil(t, paths)
-	assert.True(t, len(paths) > 1)
+	require.True(t, len(paths) > 1)
 
 	err = query.Open()
 	require.NoError(t, err)
@@ -96,7 +95,7 @@ func TestWinPerformanceQueryImplIntegration(t *testing.T) {
 	counterPath = "\\Process(*)\\% Processor Time"
 	hCounter, err = query.AddEnglishCounterToQuery(counterPath)
 	require.NoError(t, err)
-	assert.NotEqual(t, 0, hCounter)
+	require.NotEqual(t, 0, hCounter)
 
 	err = query.CollectData()
 	require.NoError(t, err)
@@ -111,7 +110,7 @@ func TestWinPerformanceQueryImplIntegration(t *testing.T) {
 		arr, err = query.GetFormattedCounterArrayDouble(hCounter)
 	}
 	require.NoError(t, err)
-	assert.True(t, len(arr) > 0, "Too")
+	require.True(t, len(arr) > 0, "Too")
 
 	err = query.Close()
 	require.NoError(t, err)
@@ -566,11 +565,11 @@ func TestWinPerfcountersCollect1Integration(t *testing.T) {
 	time.Sleep(2000 * time.Millisecond)
 	err = m.Gather(&acc)
 	require.NoError(t, err)
-	assert.Len(t, acc.Metrics, 2)
+	require.Len(t, acc.Metrics, 2)
 
 	for _, metric := range acc.Metrics {
 		_, ok := metric.Fields[expectedCounter]
-		assert.True(t, ok)
+		require.True(t, ok)
 	}
 
 }
@@ -613,11 +612,11 @@ func TestWinPerfcountersCollect2Integration(t *testing.T) {
 	err = m.Gather(&acc)
 	require.NoError(t, err)
 
-	assert.Len(t, acc.Metrics, 4)
+	require.Len(t, acc.Metrics, 4)
 
 	for _, metric := range acc.Metrics {
 		_, ok := metric.Fields[expectedCounter]
-		assert.True(t, ok)
+		require.True(t, ok)
 	}
 
 }
diff --git a/plugins/inputs/win_perf_counters/win_perf_counters_test.go b/plugins/inputs/win_perf_counters/win_perf_counters_test.go
index 969b518d0..998423e79 100644
--- a/plugins/inputs/win_perf_counters/win_perf_counters_test.go
+++ b/plugins/inputs/win_perf_counters/win_perf_counters_test.go
@@ -9,10 +9,10 @@ import (
 	"testing"
 	"time"
 
+	"github.com/stretchr/testify/require"
+
 	"github.com/influxdata/telegraf/config"
 	"github.com/influxdata/telegraf/testutil"
-	"github.com/stretchr/testify/assert"
-	"github.com/stretchr/testify/require"
 )
 
 type testCounter struct {
@@ -237,7 +237,7 @@ func TestCounterPathParsing(t *testing.T) {
 	for path, vals := range counterPathsAndRes {
 		o, i, c, err := extractCounterInfoFromCounterPath(path)
 		require.NoError(t, err)
-		require.True(t, assert.ObjectsAreEqual(vals, []string{o, i, c}), "arrays: %#v and %#v are not equal", vals, []string{o, i, c})
+		require.Equalf(t, vals, []string{o, i, c}, "arrays: %#v and %#v are not equal", vals, []string{o, i, c})
 	}
 	for _, path := range invalidCounterPaths {
 		_, _, _, err := extractCounterInfoFromCounterPath(path)
@@ -312,7 +312,7 @@ func TestParseConfigBasic(t *testing.T) {
 	require.NoError(t, err)
 	err = m.ParseConfig()
 	require.NoError(t, err)
-	assert.Len(t, m.counters, 4)
+	require.Len(t, m.counters, 4)
 	err = m.query.Close()
 	require.NoError(t, err)
 
@@ -323,7 +323,7 @@ func TestParseConfigBasic(t *testing.T) {
 	require.NoError(t, err)
 	err = m.ParseConfig()
 	require.NoError(t, err)
-	assert.Len(t, m.counters, 4)
+	require.Len(t, m.counters, 4)
 	err = m.query.Close()
 	require.NoError(t, err)
 }
@@ -349,7 +349,7 @@ func TestParseConfigNoInstance(t *testing.T) {
 	require.NoError(t, err)
 	err = m.ParseConfig()
 	require.NoError(t, err)
-	assert.Len(t, m.counters, 2)
+	require.Len(t, m.counters, 2)
 	err = m.query.Close()
 	require.NoError(t, err)
 
@@ -360,7 +360,7 @@ func TestParseConfigNoInstance(t *testing.T) {
 	require.NoError(t, err)
 	err = m.ParseConfig()
 	require.NoError(t, err)
-	assert.Len(t, m.counters, 2)
+	require.Len(t, m.counters, 2)
 	err = m.query.Close()
 	require.NoError(t, err)
 }
@@ -456,7 +456,7 @@ func TestParseConfigTotalExpansion(t *testing.T) {
 	require.NoError(t, err)
 	err = m.ParseConfig()
 	require.NoError(t, err)
-	assert.Len(t, m.counters, 4)
+	require.Len(t, m.counters, 4)
 	err = m.query.Close()
 	require.NoError(t, err)
 
@@ -478,7 +478,7 @@ func TestParseConfigTotalExpansion(t *testing.T) {
 	require.NoError(t, err)
 	err = m.ParseConfig()
 	require.NoError(t, err)
-	assert.Len(t, m.counters, 2)
+	require.Len(t, m.counters, 2)
 	err = m.query.Close()
 	require.NoError(t, err)
 }
@@ -503,7 +503,7 @@ func TestParseConfigExpand(t *testing.T) {
 	require.NoError(t, err)
 	err = m.ParseConfig()
 	require.NoError(t, err)
-	assert.Len(t, m.counters, 4)
+	require.Len(t, m.counters, 4)
 	err = m.query.Close()
 	require.NoError(t, err)
 }
@@ -629,7 +629,7 @@ func TestSimpleGatherWithTimestamp(t *testing.T) {
 		"objectname": "O",
 	}
 	acc1.AssertContainsTaggedFields(t, measurement, fields1, tags1)
-	assert.True(t, acc1.HasTimestamp(measurement, MetricTime))
+	require.True(t, acc1.HasTimestamp(measurement, MetricTime))
 }
 
 func TestGatherError(t *testing.T) {
@@ -739,9 +739,9 @@ func TestGatherRefreshingWithExpansion(t *testing.T) {
 	}
 	var acc1 testutil.Accumulator
 	err = m.Gather(&acc1)
-	assert.Len(t, m.counters, 4)
+	require.Len(t, m.counters, 4)
 	require.NoError(t, err)
-	assert.Len(t, acc1.Metrics, 2)
+	require.Len(t, acc1.Metrics, 2)
 
 	fields1 := map[string]interface{}{
 		"C1": float32(1.1),
@@ -786,8 +786,8 @@ func TestGatherRefreshingWithExpansion(t *testing.T) {
 	//test before elapsing CounterRefreshRate counters are not refreshed
 	err = m.Gather(&acc2)
 	require.NoError(t, err)
-	assert.Len(t, m.counters, 4)
-	assert.Len(t, acc2.Metrics, 2)
+	require.Len(t, m.counters, 4)
+	require.Len(t, acc2.Metrics, 2)
 
 	acc2.AssertContainsTaggedFields(t, measurement, fields1, tags1)
 	acc2.AssertContainsTaggedFields(t, measurement, fields2, tags2)
@@ -797,7 +797,7 @@ func TestGatherRefreshingWithExpansion(t *testing.T) {
 	var acc3 testutil.Accumulator
 	err = m.Gather(&acc3)
 	require.NoError(t, err)
-	assert.Len(t, acc3.Metrics, 3)
+	require.Len(t, acc3.Metrics, 3)
 
 	acc3.AssertContainsTaggedFields(t, measurement, fields1, tags1)
 	acc3.AssertContainsTaggedFields(t, measurement, fields2, tags2)
@@ -831,9 +831,9 @@ func TestGatherRefreshingWithoutExpansion(t *testing.T) {
 		CountersRefreshInterval: config.Duration(time.Second * 10)}
 	var acc1 testutil.Accumulator
 	err = m.Gather(&acc1)
-	assert.Len(t, m.counters, 2)
+	require.Len(t, m.counters, 2)
 	require.NoError(t, err)
-	assert.Len(t, acc1.Metrics, 2)
+	require.Len(t, acc1.Metrics, 2)
 
 	fields1 := map[string]interface{}{
 		"C1": float32(1.1),
@@ -880,8 +880,8 @@ func TestGatherRefreshingWithoutExpansion(t *testing.T) {
 	//test before elapsing CounterRefreshRate counters are not refreshed
 	err = m.Gather(&acc2)
 	require.NoError(t, err)
-	assert.Len(t, m.counters, 2)
-	assert.Len(t, acc2.Metrics, 3)
+	require.Len(t, m.counters, 2)
+	require.Len(t, acc2.Metrics, 3)
 
 	acc2.AssertContainsTaggedFields(t, measurement, fields1, tags1)
 	acc2.AssertContainsTaggedFields(t, measurement, fields2, tags2)
@@ -908,7 +908,7 @@ func TestGatherRefreshingWithoutExpansion(t *testing.T) {
 	var acc3 testutil.Accumulator
 	err = m.Gather(&acc3)
 	require.NoError(t, err)
-	assert.Len(t, acc3.Metrics, 2)
+	require.Len(t, acc3.Metrics, 2)
 	fields4 := map[string]interface{}{
 		"C1": float32(1.1),
 		"C2": float32(1.2),
@@ -954,8 +954,8 @@ func TestGatherTotalNoExpansion(t *testing.T) {
 	var acc1 testutil.Accumulator
 	err = m.Gather(&acc1)
 	require.NoError(t, err)
-	assert.Len(t, m.counters, 2)
-	assert.Len(t, acc1.Metrics, 2)
+	require.Len(t, m.counters, 2)
+	require.Len(t, acc1.Metrics, 2)
 	fields1 := map[string]interface{}{
 		"C1": float32(1.1),
 		"C2": float32(1.2),
@@ -984,8 +984,8 @@ func TestGatherTotalNoExpansion(t *testing.T) {
 	var acc2 testutil.Accumulator
 	err = m.Gather(&acc2)
 	require.NoError(t, err)
-	assert.Len(t, m.counters, 2)
-	assert.Len(t, acc2.Metrics, 1)
+	require.Len(t, m.counters, 2)
+	require.Len(t, acc2.Metrics, 1)
 
 	acc2.AssertContainsTaggedFields(t, measurement, fields1, tags1)
 
@@ -1013,14 +1013,14 @@ var stringArraySingleItem = []string{
 
 func TestUTF16ToStringArray(t *testing.T) {
 	singleItem := UTF16ToStringArray(unicodeStringListSingleItem)
-	assert.True(t, assert.ObjectsAreEqual(singleItem, stringArraySingleItem), "Not equal single arrays")
+	require.Equal(t, singleItem, stringArraySingleItem, "Not equal single arrays")
 
 	noItem := UTF16ToStringArray(unicodeStringListNoItem)
-	assert.Nil(t, noItem)
+	require.Nil(t, noItem)
 
 	engStrings := UTF16ToStringArray(unicodeStringListWithEnglishChars)
-	assert.True(t, assert.ObjectsAreEqual(engStrings, stringArrayWithEnglishChars), "Not equal eng arrays")
+	require.Equal(t, engStrings, stringArrayWithEnglishChars, "Not equal eng arrays")
 
 	czechStrings := UTF16ToStringArray(unicodeStringListWithCzechChars)
-	assert.True(t, assert.ObjectsAreEqual(czechStrings, stringArrayWithCzechChars), "Not equal czech arrays")
+	require.Equal(t, czechStrings, stringArrayWithCzechChars, "Not equal czech arrays")
 }
diff --git a/plugins/inputs/win_services/win_services_test.go b/plugins/inputs/win_services/win_services_test.go
index 69a75372d..153c8dfdd 100644
--- a/plugins/inputs/win_services/win_services_test.go
+++ b/plugins/inputs/win_services/win_services_test.go
@@ -10,11 +10,11 @@ import (
 	"log"
 	"testing"
 
-	"github.com/influxdata/telegraf/testutil"
-	"github.com/stretchr/testify/assert"
 	"github.com/stretchr/testify/require"
 	"golang.org/x/sys/windows/svc"
 	"golang.org/x/sys/windows/svc/mgr"
+
+	"github.com/influxdata/telegraf/testutil"
 )
 
 //testData is DD wrapper for unit testing of WinServices
@@ -136,8 +136,8 @@ func TestBasicInfo(t *testing.T) {
 		mgrProvider: &FakeMgProvider{testErrors[0]},
 	}
 	winServices.Init()
-	assert.NotEmpty(t, winServices.SampleConfig())
-	assert.NotEmpty(t, winServices.Description())
+	require.NotEmpty(t, winServices.SampleConfig())
+	require.NotEmpty(t, winServices.Description())
 }
 
 func TestMgrErrors(t *testing.T) {
@@ -149,7 +149,7 @@ func TestMgrErrors(t *testing.T) {
 	var acc1 testutil.Accumulator
 	err := winServices.Gather(&acc1)
 	require.Error(t, err)
-	assert.Contains(t, err.Error(), testErrors[0].mgrConnectError.Error())
+	require.Contains(t, err.Error(), testErrors[0].mgrConnectError.Error())
 
 	////mgr.listServices error
 	winServices = &WinServices{
@@ -159,7 +159,7 @@ func TestMgrErrors(t *testing.T) {
 	var acc2 testutil.Accumulator
 	err = winServices.Gather(&acc2)
 	require.Error(t, err)
-	assert.Contains(t, err.Error(), testErrors[1].mgrListServicesError.Error())
+	require.Contains(t, err.Error(), testErrors[1].mgrListServicesError.Error())
 
 	////mgr.listServices error 2
 	winServices = &WinServices{
@@ -213,7 +213,7 @@ func TestGatherContainsTag(t *testing.T) {
 	winServices.Init()
 	var acc1 testutil.Accumulator
 	require.NoError(t, winServices.Gather(&acc1))
-	assert.Len(t, acc1.Errors, 0, "There should be no errors after gather")
+	require.Len(t, acc1.Errors, 0, "There should be no errors after gather")
 
 	for _, s := range testSimpleData[0].services {
 		fields := make(map[string]interface{})
diff --git a/plugins/inputs/wireguard/wireguard.go b/plugins/inputs/wireguard/wireguard.go
index ded332837..068fe8c53 100644
--- a/plugins/inputs/wireguard/wireguard.go
+++ b/plugins/inputs/wireguard/wireguard.go
@@ -2,12 +2,12 @@ package wireguard
 
 import (
 	"fmt"
-	"log"
+
+	"golang.zx2c4.com/wireguard/wgctrl"
+	"golang.zx2c4.com/wireguard/wgctrl/wgtypes"
 
 	"github.com/influxdata/telegraf"
 	"github.com/influxdata/telegraf/plugins/inputs"
-	"golang.zx2c4.com/wireguard/wgctrl"
-	"golang.zx2c4.com/wireguard/wgctrl/wgtypes"
 )
 
 const (
@@ -26,7 +26,8 @@ var (
 // Wireguard is an input that enumerates all Wireguard interfaces/devices on
 // the host, and reports gauge metrics for the device itself and its peers.
 type Wireguard struct {
-	Devices []string `toml:"devices"`
+	Devices []string        `toml:"devices"`
+	Log     telegraf.Logger `toml:"-"`
 
 	client *wgctrl.Client
 }
@@ -81,7 +82,7 @@ func (wg *Wireguard) enumerateDevices() ([]*wgtypes.Device, error) {
 	for _, name := range wg.Devices {
 		dev, err := wg.client.Device(name)
 		if err != nil {
-			log.Printf("W! [inputs.wireguard] No Wireguard device found with name %s", name)
+			wg.Log.Warnf("No Wireguard device found with name %s", name)
 			continue
 		}
 
diff --git a/plugins/inputs/wireguard/wireguard_test.go b/plugins/inputs/wireguard/wireguard_test.go
index 0cfdba75d..1eb8c308c 100644
--- a/plugins/inputs/wireguard/wireguard_test.go
+++ b/plugins/inputs/wireguard/wireguard_test.go
@@ -5,9 +5,10 @@ import (
 	"testing"
 	"time"
 
-	"github.com/influxdata/telegraf/testutil"
-	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
 	"golang.zx2c4.com/wireguard/wgctrl/wgtypes"
+
+	"github.com/influxdata/telegraf/testutil"
 )
 
 func TestWireguard_gatherDeviceMetrics(t *testing.T) {
@@ -36,7 +37,7 @@ func TestWireguard_gatherDeviceMetrics(t *testing.T) {
 
 	wg.gatherDeviceMetrics(&acc, device)
 
-	assert.Equal(t, 3, acc.NFields())
+	require.Equal(t, 3, acc.NFields())
 	acc.AssertDoesNotContainMeasurement(t, measurementPeer)
 	acc.AssertContainsTaggedFields(t, measurementDevice, expectFields, expectTags)
 	acc.AssertContainsTaggedFields(t, measurementDevice, expectGauges, expectTags)
@@ -77,7 +78,7 @@ func TestWireguard_gatherDevicePeerMetrics(t *testing.T) {
 
 	wg.gatherDevicePeerMetrics(&acc, device, peer)
 
-	assert.Equal(t, 6, acc.NFields())
+	require.Equal(t, 6, acc.NFields())
 	acc.AssertDoesNotContainMeasurement(t, measurementDevice)
 	acc.AssertContainsTaggedFields(t, measurementPeer, expectFields, expectTags)
 	acc.AssertContainsTaggedFields(t, measurementPeer, expectGauges, expectTags)
diff --git a/plugins/inputs/wireless/wireless_linux.go b/plugins/inputs/wireless/wireless_linux.go
index 29a0250d9..dcca07c95 100644
--- a/plugins/inputs/wireless/wireless_linux.go
+++ b/plugins/inputs/wireless/wireless_linux.go
@@ -5,7 +5,6 @@ package wireless
 
 import (
 	"bytes"
-	"log"
 	"os"
 	"path"
 	"strconv"
@@ -51,7 +50,7 @@ func (w *Wireless) Gather(acc telegraf.Accumulator) error {
 		return err
 	}
 
-	interfaces, err := loadWirelessTable(table)
+	interfaces, err := w.loadWirelessTable(table)
 	if err != nil {
 		return err
 	}
@@ -80,8 +79,8 @@ func (w *Wireless) Gather(acc telegraf.Accumulator) error {
 	return nil
 }
 
-func loadWirelessTable(table []byte) ([]*wirelessInterface, error) {
-	var w []*wirelessInterface
+func (w *Wireless) loadWirelessTable(table []byte) ([]*wirelessInterface, error) {
+	var wi []*wirelessInterface
 	lines := bytes.Split(table, newLineByte)
 
 	// iterate over interfaces
@@ -99,10 +98,10 @@ func loadWirelessTable(table []byte) ([]*wirelessInterface, error) {
 			values = append(values, v)
 		}
 		if len(values) != interfaceFieldLength {
-			log.Printf("E! [input.wireless] invalid length of interface values")
+			w.Log.Error("invalid length of interface values")
 			continue
 		}
-		w = append(w, &wirelessInterface{
+		wi = append(wi, &wirelessInterface{
 			Interface: strings.Trim(fields[0], ":"),
 			Status:    values[0],
 			Link:      values[1],
@@ -116,7 +115,7 @@ func loadWirelessTable(table []byte) ([]*wirelessInterface, error) {
 			Beacon:    values[9],
 		})
 	}
-	return w, nil
+	return wi, nil
 }
 
 // loadPath can be used to read path firstly from config
@@ -128,13 +127,13 @@ func (w *Wireless) loadPath() {
 }
 
 // proc can be used to read file paths from env
-func proc(env, path string) string {
+func proc(env, defaultPath string) string {
 	// try to read full file path
 	if p := os.Getenv(env); p != "" {
 		return p
 	}
 	// return default path
-	return path
+	return defaultPath
 }
 
 func init() {
diff --git a/plugins/inputs/wireless/wireless_test.go b/plugins/inputs/wireless/wireless_test.go
index 20c10de88..dbf2f7aea 100644
--- a/plugins/inputs/wireless/wireless_test.go
+++ b/plugins/inputs/wireless/wireless_test.go
@@ -6,7 +6,9 @@ package wireless
 import (
 	"testing"
 
-	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+
+	"github.com/influxdata/telegraf/testutil"
 )
 
 var testInput = []byte(`Inter-| sta-|   Quality        |   Discarded packets               | Missed | WE
@@ -43,11 +45,13 @@ func TestLoadWirelessTable(t *testing.T) {
 			Beacon:    int64(0),
 		},
 	}
-	metrics, err := loadWirelessTable(testInput)
-	if err != nil {
-		t.Fatal(err)
-	}
 
-	as := assert.New(t)
+	w := Wireless{
+		Log: testutil.Logger{},
+	}
+	metrics, err := w.loadWirelessTable(testInput)
+	require.NoError(t, err)
+
+	as := require.New(t)
 	as.Equal(metrics, expectedMetrics)
 }
diff --git a/plugins/inputs/x509_cert/x509_cert_test.go b/plugins/inputs/x509_cert/x509_cert_test.go
index f0b037910..8e6ece05f 100644
--- a/plugins/inputs/x509_cert/x509_cert_test.go
+++ b/plugins/inputs/x509_cert/x509_cert_test.go
@@ -14,8 +14,6 @@ import (
 	"time"
 
 	"github.com/pion/dtls/v2"
-
-	"github.com/stretchr/testify/assert"
 	"github.com/stretchr/testify/require"
 
 	"github.com/influxdata/telegraf"
@@ -199,30 +197,28 @@ func TestTags(t *testing.T) {
 	acc := testutil.Accumulator{}
 	require.NoError(t, sc.Gather(&acc))
 
-	assert.True(t, acc.HasMeasurement("x509_cert"))
+	require.True(t, acc.HasMeasurement("x509_cert"))
 
-	assert.True(t, acc.HasTag("x509_cert", "common_name"))
-	assert.Equal(t, "server.localdomain", acc.TagValue("x509_cert", "common_name"))
+	require.True(t, acc.HasTag("x509_cert", "common_name"))
+	require.Equal(t, "server.localdomain", acc.TagValue("x509_cert", "common_name"))
 
-	assert.True(t, acc.HasTag("x509_cert", "signature_algorithm"))
-	assert.Equal(t, "SHA256-RSA", acc.TagValue("x509_cert", "signature_algorithm"))
+	require.True(t, acc.HasTag("x509_cert", "signature_algorithm"))
+	require.Equal(t, "SHA256-RSA", acc.TagValue("x509_cert", "signature_algorithm"))
 
-	assert.True(t, acc.HasTag("x509_cert", "public_key_algorithm"))
-	assert.Equal(t, "RSA", acc.TagValue("x509_cert", "public_key_algorithm"))
+	require.True(t, acc.HasTag("x509_cert", "public_key_algorithm"))
+	require.Equal(t, "RSA", acc.TagValue("x509_cert", "public_key_algorithm"))
 
-	assert.True(t, acc.HasTag("x509_cert", "issuer_common_name"))
-	assert.Equal(t, "Telegraf Test CA", acc.TagValue("x509_cert", "issuer_common_name"))
+	require.True(t, acc.HasTag("x509_cert", "issuer_common_name"))
+	require.Equal(t, "Telegraf Test CA", acc.TagValue("x509_cert", "issuer_common_name"))
 
-	assert.True(t, acc.HasTag("x509_cert", "san"))
-	assert.Equal(t, "localhost,127.0.0.1", acc.TagValue("x509_cert", "san"))
+	require.True(t, acc.HasTag("x509_cert", "san"))
+	require.Equal(t, "localhost,127.0.0.1", acc.TagValue("x509_cert", "san"))
 
-	assert.True(t, acc.HasTag("x509_cert", "serial_number"))
+	require.True(t, acc.HasTag("x509_cert", "serial_number"))
 	serialNumber := new(big.Int)
 	_, validSerialNumber := serialNumber.SetString(acc.TagValue("x509_cert", "serial_number"), 16)
-	if !validSerialNumber {
-		t.Errorf("Expected a valid Hex serial number but got %s", acc.TagValue("x509_cert", "serial_number"))
-	}
-	assert.Equal(t, big.NewInt(1), serialNumber)
+	require.Truef(t, validSerialNumber, "Expected a valid Hex serial number but got %s", acc.TagValue("x509_cert", "serial_number"))
+	require.Equal(t, big.NewInt(1), serialNumber)
 }
 
 func TestGatherChain(t *testing.T) {
@@ -288,8 +284,8 @@ func TestGatherUDPCert(t *testing.T) {
 	var acc testutil.Accumulator
 	require.NoError(t, m.Gather(&acc))
 
-	assert.Len(t, acc.Errors, 0)
-	assert.True(t, acc.HasMeasurement("x509_cert"))
+	require.Len(t, acc.Errors, 0)
+	require.True(t, acc.HasMeasurement("x509_cert"))
 }
 
 func TestStrings(t *testing.T) {
@@ -328,7 +324,7 @@ func TestGatherCertIntegration(t *testing.T) {
 	var acc testutil.Accumulator
 	require.NoError(t, m.Gather(&acc))
 
-	assert.True(t, acc.HasMeasurement("x509_cert"))
+	require.True(t, acc.HasMeasurement("x509_cert"))
 }
 
 func TestGatherCertMustNotTimeout(t *testing.T) {
@@ -345,7 +341,7 @@ func TestGatherCertMustNotTimeout(t *testing.T) {
 	var acc testutil.Accumulator
 	require.NoError(t, m.Gather(&acc))
 	require.Empty(t, acc.Errors)
-	assert.True(t, acc.HasMeasurement("x509_cert"))
+	require.True(t, acc.HasMeasurement("x509_cert"))
 }
 
 func TestSourcesToURLs(t *testing.T) {
@@ -354,8 +350,8 @@ func TestSourcesToURLs(t *testing.T) {
 	}
 	require.NoError(t, m.Init())
 
-	assert.Equal(t, len(m.globpaths), 2)
-	assert.Equal(t, len(m.locations), 2)
+	require.Equal(t, len(m.globpaths), 2)
+	require.Equal(t, len(m.locations), 2)
 }
 
 func TestServerName(t *testing.T) {
@@ -385,11 +381,11 @@ func TestServerName(t *testing.T) {
 			require.NoError(t, err)
 			actual, err := sc.serverName(u)
 			if test.err {
-				assert.Error(t, err)
+				require.Error(t, err)
 			} else {
-				assert.NoError(t, err)
+				require.NoError(t, err)
 			}
-			assert.Equal(t, test.expected, actual)
+			require.Equal(t, test.expected, actual)
 		})
 	}
 }
diff --git a/plugins/inputs/zipkin/zipkin.go b/plugins/inputs/zipkin/zipkin.go
index e679de5c4..c230736ad 100644
--- a/plugins/inputs/zipkin/zipkin.go
+++ b/plugins/inputs/zipkin/zipkin.go
@@ -9,6 +9,7 @@ import (
 	"sync"
 
 	"github.com/gorilla/mux"
+
 	"github.com/influxdata/telegraf"
 	"github.com/influxdata/telegraf/plugins/inputs"
 	"github.com/influxdata/telegraf/plugins/inputs/zipkin/trace"
@@ -108,8 +109,8 @@ func (z *Zipkin) Start(acc telegraf.Accumulator) error {
 	z.address = ln.Addr().String()
 	z.Log.Infof("Started the zipkin listener on %s", z.address)
 
+	wg.Add(1)
 	go func() {
-		wg.Add(1)
 		defer wg.Done()
 
 		z.Listen(ln, acc)
@@ -140,7 +141,7 @@ func (z *Zipkin) Listen(ln net.Listener, acc telegraf.Accumulator) {
 		// This interferes with telegraf's internal data collection,
 		// by making it appear as if a serious error occurred.
 		if err != http.ErrServerClosed {
-			acc.AddError(fmt.Errorf("E! Error listening: %v", err))
+			acc.AddError(fmt.Errorf("error listening: %v", err))
 		}
 	}
 }
diff --git a/plugins/inputs/zipkin/zipkin_test.go b/plugins/inputs/zipkin/zipkin_test.go
index 0c0bab279..f2f07c572 100644
--- a/plugins/inputs/zipkin/zipkin_test.go
+++ b/plugins/inputs/zipkin/zipkin_test.go
@@ -9,6 +9,7 @@ import (
 	"time"
 
 	"github.com/google/go-cmp/cmp"
+
 	"github.com/influxdata/telegraf"
 	"github.com/influxdata/telegraf/testutil"
 )
@@ -649,10 +650,12 @@ func postThriftData(datafile, address, contentType string) error {
 
 	req.Header.Set("Content-Type", contentType)
 	client := &http.Client{}
-	_, err = client.Do(req)
+	resp, err := client.Do(req)
 	if err != nil {
 		return fmt.Errorf("HTTP POST request to zipkin endpoint %s failed %v", address, err)
 	}
 
+	defer resp.Body.Close()
+
 	return nil
 }
diff --git a/plugins/inputs/zookeeper/zookeeper_test.go b/plugins/inputs/zookeeper/zookeeper_test.go
index bbc2a37cb..f2e3edcf7 100644
--- a/plugins/inputs/zookeeper/zookeeper_test.go
+++ b/plugins/inputs/zookeeper/zookeeper_test.go
@@ -3,9 +3,9 @@ package zookeeper
 import (
 	"testing"
 
-	"github.com/influxdata/telegraf/testutil"
-	"github.com/stretchr/testify/assert"
 	"github.com/stretchr/testify/require"
+
+	"github.com/influxdata/telegraf/testutil"
 )
 
 func TestZookeeperGeneratesMetricsIntegration(t *testing.T) {
@@ -37,6 +37,6 @@ func TestZookeeperGeneratesMetricsIntegration(t *testing.T) {
 	}
 
 	for _, metric := range intMetrics {
-		assert.True(t, acc.HasInt64Field("zookeeper", metric), metric)
+		require.True(t, acc.HasInt64Field("zookeeper", metric), metric)
 	}
 }