refactor: Create testutil.OverrideStdin test helper method.

internal/tailer/logstream/logstream_unix_test.go

@@ -16,16 +16,12 @@ import (
 func TestReadStdin(t *testing.T) {
 	ctx := context.Background()
 	var wg sync.WaitGroup
-	// Need to pretend Stdin is a fifo for this to pass.
-	oldStdin := os.Stdin
-	t.Cleanup(func() { os.Stdin = oldStdin })
-
 	tmpDir := testutil.TestTempDir(t)
 	name := filepath.Join(tmpDir, "fakeStdin")
 	testutil.FatalIfErr(t, unix.Mkfifo(name, 0o666))
-	var err error
-	os.Stdin, err = os.OpenFile(name, os.O_RDWR, os.ModeNamedPipe)
+	f, err := os.OpenFile(name, os.O_RDWR, os.ModeNamedPipe)
 	testutil.FatalIfErr(t, err)
+	testutil.OverrideStdin(t, f)
 
 	_, err = New(ctx, &wg, nil, "-", nil, false)
 	if err != nil {

internal/tailer/logstream/pipestream_unix_test.go

@@ -153,16 +153,10 @@ func TestPipeStreamReadStdin(t *testing.T) {
 
 	name := filepath.Join(tmpDir, "fakestdin")
 	testutil.FatalIfErr(t, unix.Mkfifo(name, 0o666))
-
-	oldStdin := os.Stdin
-	t.Cleanup(func() {
-		os.Stdin = oldStdin
-	})
-
-	var err error
-	os.Stdin, err = os.OpenFile(name, os.O_RDWR, os.ModeNamedPipe)
+	f, err := os.OpenFile(name, os.O_RDWR, os.ModeNamedPipe)
 	testutil.FatalIfErr(t, err)
-	testutil.WriteString(t, os.Stdin, "content\n")
+	testutil.OverrideStdin(t, f)
+	testutil.WriteString(t, f, "content\n")
 
 	lines := make(chan *logline.LogLine, 1)
 	ctx, cancel := context.WithCancel(context.Background())
@@ -173,7 +167,7 @@ func TestPipeStreamReadStdin(t *testing.T) {
 
 	awaken(0)
 
-	testutil.FatalIfErr(t, os.Stdin.Close())
+	testutil.FatalIfErr(t, f.Close())
 
 	cancel()
 

internal/tailer/tail_unix_test.go

@@ -75,16 +75,10 @@ func TestAddStdin(t *testing.T) {
 
 	name := filepath.Join(ta.tmpDir, "fakestdin")
 	testutil.FatalIfErr(t, unix.Mkfifo(name, 0o666))
-
-	oldStdin := os.Stdin
-	t.Cleanup(func() {
-		os.Stdin = oldStdin
-	})
-
-	var err error
-	os.Stdin, err = os.OpenFile(name, os.O_RDWR, os.ModeNamedPipe)
+	f, err := os.OpenFile(name, os.O_RDWR, os.ModeNamedPipe)
 	testutil.FatalIfErr(t, err)
-	testutil.WriteString(t, os.Stdin, "content\n")
+	testutil.OverrideStdin(t, f)
+	testutil.WriteString(t, f, "content\n")
 
 	if err := ta.AddPattern("-"); err != nil {
 		t.Errorf("AddPattern(-) -> %v", err)

internal/testutil/stdin.go

@@ -0,0 +1,17 @@
+package testutil
+
+import (
+	"os"
+	"testing"
+)
+
+// OverrideStdin replaces standard input with another *os.File and restores
+// it at the end of the test.
+func OverrideStdin(tb testing.TB, fakeStdin *os.File) {
+	tb.Helper()
+	oldStdin := os.Stdin
+	tb.Cleanup(func() {
+		os.Stdin = oldStdin
+	})
+	os.Stdin = fakeStdin
+}