Implement testing.TB.Chdir, added in go 1.24

fake_coverage_test.go

@@ -37,7 +37,7 @@ func TestTBCoverage(t *testing.T) {
 
 		mn := m.Name
 		// TODO(prashant): Implement new methods added in 1.24 before release.
-		if mn == "Chdir" || mn == "Context" {
+		if mn == "Context" {
 			continue
 		}
 		if _, ok := ftSet[mn]; !ok {

fake_tb.go

@@ -3,6 +3,7 @@ package faket
 import (
 	"fmt"
 	"os"
+	"path/filepath"
 	"runtime"
 	"strings"
 	"sync"
@@ -415,3 +416,37 @@ func (tb *fakeTB) TempDir() string {
 
 	return d
 }
+
+func (tb *fakeTB) Chdir(dir string) {
+	oldWd, err := os.Open(".")
+	if err != nil {
+		// Match stdlib error.
+		tb.Fatal(err)
+	}
+	if err := os.Chdir(dir); err != nil {
+		// Match stdlib error.
+		tb.Fatal(err)
+	}
+
+	// Similar to stdlib, on POSIX, set PWD.
+	switch runtime.GOOS {
+	case "windows", "plan9":
+		// Windows and Plan 9 do not use the PWD variable.
+	default:
+		if !filepath.IsAbs(dir) {
+			dir, err = os.Getwd()
+			if err != nil {
+				tb.Fatal(err)
+			}
+		}
+		tb.Setenv("PWD", dir)
+	}
+
+	tb.Cleanup(func() {
+		defer oldWd.Close() //nolint:errcheck // best-effort close to avoid leaks.
+		if err := oldWd.Chdir(); err != nil {
+			// Note: The stdlib implementation panics here, but we avoid panics.
+			tb.Errorf("ChDir failed to ChDir to original directory: %v", err)
+		}
+	})
+}

integration_1_24_test.go

@@ -0,0 +1,60 @@
+//go:build go1.24
+
+package faket_test
+
+import (
+	"os"
+	"regexp"
+	"strings"
+	"testing"
+
+	"github.com/prashantv/faket/internal/cmptest"
+	"github.com/prashantv/faket/internal/want"
+)
+
+func TestCmp_Chdir(t *testing.T) {
+	t.Run("to non-existent", func(t *testing.T) {
+		// ChDir failures are reported by testing.go in stdlib
+		// and similarly fake_tb.go with faket.
+		opts := cmptest.Opts{
+			LogReplace: func(s string) string {
+				s = regexp.MustCompile("testing.go:[0-9]+").ReplaceAllString(s, "testing.go:Chdir")
+				s = strings.ReplaceAll(s, "fake_tb.go:428", "testing.go:Chdir")
+				return s
+			},
+		}
+		cmptest.CompareOpts(t, opts, func(t testing.TB) {
+			t.Chdir("./does/not/exist")
+			t.Log("skipped (due to fatal in ChDir)")
+		})
+	})
+
+	mustGetWd := func() string {
+		wd, err := os.Getwd()
+		want.NoErr(t, err)
+		return wd
+	}
+
+	initialWD := mustGetWd()
+	initialPWD := os.Getenv("PWD")
+
+	stripWD := func(s string) string {
+		return strings.ReplaceAll(s, initialWD, "/path/to/faket")
+	}
+
+	t.Run("success", func(t *testing.T) {
+		cmptest.Compare(t, func(t testing.TB) {
+			t.Chdir("./testdata")
+
+			wd, err := os.Getwd()
+			want.NoErr(t, err)
+			t.Log("wd is", stripWD(wd))
+			t.Log("PWD is", stripWD(os.Getenv("PWD")))
+		})
+	})
+
+	postWD := mustGetWd()
+	postPWD := os.Getenv("PWD")
+	want.Equal(t, "Getwd", postWD, initialWD)
+	want.Equal(t, "PWD", postPWD, initialPWD)
+}

internal/cmptest/cmptest.go

@@ -63,7 +63,8 @@ func Compare(t *testing.T, f func(testing.TB)) {
 
 // Opts are options for comparing faket to a real test run.
 type Opts struct {
-	WantPanic bool
+	WantPanic  bool
+	LogReplace func(string) string
 }
 
 // CompareOpts is the same as Compare, but supports options for customizing comparisons.
@@ -127,7 +128,14 @@ func CompareOpts(t *testing.T, opts Opts, f func(t testing.TB)) {
 		}
 	}
 
+	wantLogs := wantOutput.String()
+	gotLogs := logs.String()
+	if opts.LogReplace != nil {
+		wantLogs = opts.LogReplace(wantLogs)
+		gotLogs = opts.LogReplace(gotLogs)
+	}
+
 	want.Equal(t, "result event", resultEvent, true)
-	want.Equal(t, "log output", logs.String(), wantOutput.String())
+	want.Equal(t, "log output", gotLogs, wantLogs)
 	want.Equal(t, "panicked", res.Panicked(), opts.WantPanic)
 }

internal/panictests/p1/testdata/cmp_test_results.json

@@ -16,8 +16,8 @@
 {"Time":"2022-06-11T00:00:00.0Z","Action":"output","Package":"github.com/prashantv/faket/internal/panictests/p1","Test":"TestCmp_Panic","Output":"\truntime/panic.go:1 +0x0000\n"}
 {"Time":"2022-06-11T00:00:00.0Z","Action":"output","Package":"github.com/prashantv/faket/internal/panictests/p1","Test":"TestCmp_Panic","Output":"github.com/prashantv/faket/internal/panictests/p1.TestCmp_Panic.func1({0x0000, 0x0000})\n"}
 {"Time":"2022-06-11T00:00:00.0Z","Action":"output","Package":"github.com/prashantv/faket/internal/panictests/p1","Test":"TestCmp_Panic","Output":"\tgithub.com/prashantv/faket/internal/panictests/p1/panic_1_test.go:15 +0x0000\n"}
-{"Time":"2022-06-11T00:00:00.0Z","Action":"output","Package":"github.com/prashantv/faket/internal/panictests/p1","Test":"TestCmp_Panic","Output":"github.com/prashantv/faket/internal/cmptest.CompareOpts(0x0000, {0x0000?}, 0x0000?)\n"}
-{"Time":"2022-06-11T00:00:00.0Z","Action":"output","Package":"github.com/prashantv/faket/internal/panictests/p1","Test":"TestCmp_Panic","Output":"\tgithub.com/prashantv/faket/internal/cmptest/cmptest.go:77 +0x0000\n"}
+{"Time":"2022-06-11T00:00:00.0Z","Action":"output","Package":"github.com/prashantv/faket/internal/panictests/p1","Test":"TestCmp_Panic","Output":"github.com/prashantv/faket/internal/cmptest.CompareOpts(0x0000, {0x0000?, 0x0000?}, 0x0000?)\n"}
+{"Time":"2022-06-11T00:00:00.0Z","Action":"output","Package":"github.com/prashantv/faket/internal/panictests/p1","Test":"TestCmp_Panic","Output":"\tgithub.com/prashantv/faket/internal/cmptest/cmptest.go:78 +0x0000\n"}
 {"Time":"2022-06-11T00:00:00.0Z","Action":"output","Package":"github.com/prashantv/faket/internal/panictests/p1","Test":"TestCmp_Panic","Output":"github.com/prashantv/faket/internal/panictests/p1.TestCmp_Panic(0x0000?)\n"}
 {"Time":"2022-06-11T00:00:00.0Z","Action":"output","Package":"github.com/prashantv/faket/internal/panictests/p1","Test":"TestCmp_Panic","Output":"\tgithub.com/prashantv/faket/internal/panictests/p1/panic_1_test.go:11 +0x0000\n"}
 {"Time":"2022-06-11T00:00:00.0Z","Action":"output","Package":"github.com/prashantv/faket/internal/panictests/p1","Test":"TestCmp_Panic","Output":"testing.tRunner(0x0000, 0x0000)\n"}

testdata/cmp_test_results.json

@@ -1,4 +1,19 @@
 {"Time":"2022-06-11T00:00:00.0Z","Action":"start","Package":"github.com/prashantv/faket"}
+{"Time":"2022-06-11T00:00:00.0Z","Action":"run","Package":"github.com/prashantv/faket","Test":"TestCmp_Chdir"}
+{"Time":"2022-06-11T00:00:00.0Z","Action":"output","Package":"github.com/prashantv/faket","Test":"TestCmp_Chdir","Output":"=== RUN   TestCmp_Chdir\n"}
+{"Time":"2022-06-11T00:00:00.0Z","Action":"run","Package":"github.com/prashantv/faket","Test":"TestCmp_Chdir/to_non-existent"}
+{"Time":"2022-06-11T00:00:00.0Z","Action":"output","Package":"github.com/prashantv/faket","Test":"TestCmp_Chdir/to_non-existent","Output":"=== RUN   TestCmp_Chdir/to_non-existent\n"}
+{"Time":"2022-06-11T00:00:00.0Z","Action":"output","Package":"github.com/prashantv/faket","Test":"TestCmp_Chdir/to_non-existent","Output":"    testing.go:1358: chdir ./does/not/exist: no such file or directory\n"}
+{"Time":"2022-06-11T00:00:00.0Z","Action":"run","Package":"github.com/prashantv/faket","Test":"TestCmp_Chdir/success"}
+{"Time":"2022-06-11T00:00:00.0Z","Action":"output","Package":"github.com/prashantv/faket","Test":"TestCmp_Chdir/success","Output":"=== RUN   TestCmp_Chdir/success\n"}
+{"Time":"2022-06-11T00:00:00.0Z","Action":"output","Package":"github.com/prashantv/faket","Test":"TestCmp_Chdir/success","Output":"    integration_1_24_test.go:51: wd is /path/to/faket/testdata\n"}
+{"Time":"2022-06-11T00:00:00.0Z","Action":"output","Package":"github.com/prashantv/faket","Test":"TestCmp_Chdir/success","Output":"    integration_1_24_test.go:52: PWD is /path/to/faket/testdata\n"}
+{"Time":"2022-06-11T00:00:00.0Z","Action":"output","Package":"github.com/prashantv/faket","Test":"TestCmp_Chdir","Output":"--- FAIL: TestCmp_Chdir (0.01s)\n"}
+{"Time":"2022-06-11T00:00:00.0Z","Action":"output","Package":"github.com/prashantv/faket","Test":"TestCmp_Chdir/to_non-existent","Output":"    --- FAIL: TestCmp_Chdir/to_non-existent (0.01s)\n"}
+{"Time":"2022-06-11T00:00:00.0Z","Action":"fail","Package":"github.com/prashantv/faket","Test":"TestCmp_Chdir/to_non-existent","Elapsed":0}
+{"Time":"2022-06-11T00:00:00.0Z","Action":"output","Package":"github.com/prashantv/faket","Test":"TestCmp_Chdir/success","Output":"    --- PASS: TestCmp_Chdir/success (0.01s)\n"}
+{"Time":"2022-06-11T00:00:00.0Z","Action":"pass","Package":"github.com/prashantv/faket","Test":"TestCmp_Chdir/success","Elapsed":0}
+{"Time":"2022-06-11T00:00:00.0Z","Action":"fail","Package":"github.com/prashantv/faket","Test":"TestCmp_Chdir","Elapsed":0}
 {"Time":"2022-06-11T00:00:00.0Z","Action":"run","Package":"github.com/prashantv/faket","Test":"TestCmp_Success"}
 {"Time":"2022-06-11T00:00:00.0Z","Action":"output","Package":"github.com/prashantv/faket","Test":"TestCmp_Success","Output":"=== RUN   TestCmp_Success\n"}
 {"Time":"2022-06-11T00:00:00.0Z","Action":"output","Package":"github.com/prashantv/faket","Test":"TestCmp_Success","Output":"    integration_test.go:20: log1\n"}