src/cmd/cover/cover_test.go - go - Git at Google

 // Copyright 2013 The Go Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.

 package main_test

 import (
 	"bufio"
 	"bytes"
 	"flag"
 	"fmt"
 	"go/ast"
 	"go/parser"
 	"go/token"
 	"internal/testenv"
 	"os"
 	"os/exec"
 	"path/filepath"
 	"regexp"
 	"strings"
 	"sync"
 	"testing"
 )

 const (
 	// Data directory, also the package directory for the test.
 	testdata = "testdata"
 )

 var (
 	// Input files.
 	testMain       = filepath.Join(testdata, "main.go")
 	testTest       = filepath.Join(testdata, "test.go")
 	coverProfile   = filepath.Join(testdata, "profile.cov")
 	toolexecSource = filepath.Join(testdata, "toolexec.go")

 	// The HTML test files are in a separate directory
 	// so they are a complete package.
 	htmlGolden = filepath.Join(testdata, "html", "html.golden")

 	// Temporary files.
 	tmpTestMain    string
 	coverInput     string
 	coverOutput    string
 	htmlProfile    string
 	htmlHTML       string
 	htmlUDir       string
 	htmlU          string
 	htmlUTest      string
 	htmlUProfile   string
 	htmlUHTML      string
 	lineDupDir     string
 	lineDupGo      string
 	lineDupTestGo  string
 	lineDupProfile string
 )

 var (
 	// testTempDir is a temporary directory created in TestMain.
 	testTempDir string

 	// testcover is a newly built version of the cover program.
 	testcover string

 	// toolexec is a program to use as the go tool's -toolexec argument.
 	toolexec string

 	// testcoverErr records an error building testcover or toolexec.
 	testcoverErr error

 	// testcoverOnce is used to build testcover once.
 	testcoverOnce sync.Once

 	// toolexecArg is the argument to pass to the go tool.
 	toolexecArg string
 )

 var debug = flag.Bool("debug", false, "keep rewritten files for debugging")

 // We use TestMain to set up a temporary directory and remove it when
 // the tests are done.
 func TestMain(m *testing.M) {
 	dir, err := os.MkdirTemp("", "go-testcover")
 	if err != nil {
 		fmt.Fprintln(os.Stderr, err)
 		os.Exit(1)
 	}
 	os.Setenv("GOPATH", filepath.Join(dir, "_gopath"))

 	testTempDir = dir

 	tmpTestMain = filepath.Join(dir, "main.go")
 	coverInput = filepath.Join(dir, "test_line.go")
 	coverOutput = filepath.Join(dir, "test_cover.go")
 	htmlProfile = filepath.Join(dir, "html.cov")
 	htmlHTML = filepath.Join(dir, "html.html")
 	htmlUDir = filepath.Join(dir, "htmlunformatted")
 	htmlU = filepath.Join(htmlUDir, "htmlunformatted.go")
 	htmlUTest = filepath.Join(htmlUDir, "htmlunformatted_test.go")
 	htmlUProfile = filepath.Join(htmlUDir, "htmlunformatted.cov")
 	htmlUHTML = filepath.Join(htmlUDir, "htmlunformatted.html")
 	lineDupDir = filepath.Join(dir, "linedup")
 	lineDupGo = filepath.Join(lineDupDir, "linedup.go")
 	lineDupTestGo = filepath.Join(lineDupDir, "linedup_test.go")
 	lineDupProfile = filepath.Join(lineDupDir, "linedup.out")

 	status := m.Run()

 	if !*debug {
 		os.RemoveAll(dir)
 	}

 	os.Exit(status)
 }

 // buildCover builds a version of the cover program for testing.
 // This ensures that "go test cmd/cover" tests the current cmd/cover.
 func buildCover(t *testing.T) {
 	t.Helper()
 	testenv.MustHaveGoBuild(t)
 	testcoverOnce.Do(func() {
 		var wg sync.WaitGroup
 		wg.Add(2)

 		var err1, err2 error
 		go func() {
 			defer wg.Done()
 			testcover = filepath.Join(testTempDir, "cover.exe")
 			t.Logf("running [go build -o %s]", testcover)
 			out, err := exec.Command(testenv.GoToolPath(t), "build", "-o", testcover).CombinedOutput()
 			if len(out) > 0 {
 				t.Logf("%s", out)
 			}
 			err1 = err
 		}()

 		go func() {
 			defer wg.Done()
 			toolexec = filepath.Join(testTempDir, "toolexec.exe")
 			t.Logf("running [go -build -o %s %s]", toolexec, toolexecSource)
 			out, err := exec.Command(testenv.GoToolPath(t), "build", "-o", toolexec, toolexecSource).CombinedOutput()
 			if len(out) > 0 {
 				t.Logf("%s", out)
 			}
 			err2 = err
 		}()

 		wg.Wait()

 		testcoverErr = err1
 		if err2 != nil && err1 == nil {
 			testcoverErr = err2
 		}

 		toolexecArg = "-toolexec=" + toolexec + " " + testcover
 	})
 	if testcoverErr != nil {
 		t.Fatal("failed to build testcover or toolexec program:", testcoverErr)
 	}
 }

 // Run this shell script, but do it in Go so it can be run by "go test".
 //
 //	replace the word LINE with the line number < testdata/test.go > testdata/test_line.go
 // 	go build -o testcover
 // 	testcover -mode=count -var=CoverTest -o ./testdata/test_cover.go testdata/test_line.go
 //	go run ./testdata/main.go ./testdata/test.go
 //
 func TestCover(t *testing.T) {
 	t.Parallel()
 	testenv.MustHaveGoRun(t)
 	buildCover(t)

 	// Read in the test file (testTest) and write it, with LINEs specified, to coverInput.
 	file, err := os.ReadFile(testTest)
 	if err != nil {
 		t.Fatal(err)
 	}
 	lines := bytes.Split(file, []byte("\n"))
 	for i, line := range lines {
 		lines[i] = bytes.ReplaceAll(line, []byte("LINE"), []byte(fmt.Sprint(i+1)))
 	}

 	// Add a function that is not gofmt'ed. This used to cause a crash.
 	// We don't put it in test.go because then we would have to gofmt it.
 	// Issue 23927.
 	lines = append(lines, []byte("func unFormatted() {"),
 		[]byte("\tif true {"),
 		[]byte("\t}else{"),
 		[]byte("\t}"),
 		[]byte("}"))
 	lines = append(lines, []byte("func unFormatted2(b bool) {if b{}else{}}"))

 	if err := os.WriteFile(coverInput, bytes.Join(lines, []byte("\n")), 0666); err != nil {
 		t.Fatal(err)
 	}

 	// testcover -mode=count -var=thisNameMustBeVeryLongToCauseOverflowOfCounterIncrementStatementOntoNextLineForTest -o ./testdata/test_cover.go testdata/test_line.go
 	cmd := exec.Command(testcover, "-mode=count", "-var=thisNameMustBeVeryLongToCauseOverflowOfCounterIncrementStatementOntoNextLineForTest", "-o", coverOutput, coverInput)
 	run(cmd, t)

 	cmd = exec.Command(testcover, "-mode=set", "-var=Not_an-identifier", "-o", coverOutput, coverInput)
 	err = cmd.Run()
 	if err == nil {
 		t.Error("Expected cover to fail with an error")
 	}

 	// Copy testmain to testTempDir, so that it is in the same directory
 	// as coverOutput.
 	b, err := os.ReadFile(testMain)
 	if err != nil {
 		t.Fatal(err)
 	}
 	if err := os.WriteFile(tmpTestMain, b, 0444); err != nil {
 		t.Fatal(err)
 	}

 	// go run ./testdata/main.go ./testdata/test.go
 	cmd = exec.Command(testenv.GoToolPath(t), "run", tmpTestMain, coverOutput)
 	run(cmd, t)

 	file, err = os.ReadFile(coverOutput)
 	if err != nil {
 		t.Fatal(err)
 	}
 	// compiler directive must appear right next to function declaration.
 	if got, err := regexp.MatchString(".*\n//go:nosplit\nfunc someFunction().*", string(file)); err != nil || !got {
 		t.Error("misplaced compiler directive")
 	}
 	// "go:linkname" compiler directive should be present.
 	if got, err := regexp.MatchString(`.*go\:linkname some\_name some\_name.*`, string(file)); err != nil || !got {
 		t.Error("'go:linkname' compiler directive not found")
 	}

 	// Other comments should be preserved too.
 	c := ".*// This comment didn't appear in generated go code.*"
 	if got, err := regexp.MatchString(c, string(file)); err != nil || !got {
 		t.Errorf("non compiler directive comment %q not found", c)
 	}
 }

 // TestDirectives checks that compiler directives are preserved and positioned
 // correctly. Directives that occur before top-level declarations should remain
 // above those declarations, even if they are not part of the block of
 // documentation comments.
 func TestDirectives(t *testing.T) {
 	t.Parallel()
 	buildCover(t)

 	// Read the source file and find all the directives. We'll keep
 	// track of whether each one has been seen in the output.
 	testDirectives := filepath.Join(testdata, "directives.go")
 	source, err := os.ReadFile(testDirectives)
 	if err != nil {
 		t.Fatal(err)
 	}
 	sourceDirectives := findDirectives(source)

 	// testcover -mode=atomic ./testdata/directives.go
 	cmd := exec.Command(testcover, "-mode=atomic", testDirectives)
 	cmd.Stderr = os.Stderr
 	output, err := cmd.Output()
 	if err != nil {
 		t.Fatal(err)
 	}

 	// Check that all directives are present in the output.
 	outputDirectives := findDirectives(output)
 	foundDirective := make(map[string]bool)
 	for _, p := range sourceDirectives {
 		foundDirective[p.name] = false
 	}
 	for _, p := range outputDirectives {
 		if found, ok := foundDirective[p.name]; !ok {
 			t.Errorf("unexpected directive in output: %s", p.text)
 		} else if found {
 			t.Errorf("directive found multiple times in output: %s", p.text)
 		}
 		foundDirective[p.name] = true
 	}
 	for name, found := range foundDirective {
 		if !found {
 			t.Errorf("missing directive: %s", name)
 		}
 	}

 	// Check that directives that start with the name of top-level declarations
 	// come before the beginning of the named declaration and after the end
 	// of the previous declaration.
 	fset := token.NewFileSet()
 	astFile, err := parser.ParseFile(fset, testDirectives, output, 0)
 	if err != nil {
 		t.Fatal(err)
 	}

 	prevEnd := 0
 	for _, decl := range astFile.Decls {
 		var name string
 		switch d := decl.(type) {
 		case *ast.FuncDecl:
 			name = d.Name.Name
 		case *ast.GenDecl:
 			if len(d.Specs) == 0 {
 				// An empty group declaration. We still want to check that
 				// directives can be associated with it, so we make up a name
 				// to match directives in the test data.
 				name = "_empty"
 			} else if spec, ok := d.Specs[0].(*ast.TypeSpec); ok {
 				name = spec.Name.Name
 			}
 		}
 		pos := fset.Position(decl.Pos()).Offset
 		end := fset.Position(decl.End()).Offset
 		if name == "" {
 			prevEnd = end
 			continue
 		}
 		for _, p := range outputDirectives {
 			if !strings.HasPrefix(p.name, name) {
 				continue
 			}
 			if p.offset < prevEnd || pos < p.offset {
 				t.Errorf("directive %s does not appear before definition %s", p.text, name)
 			}
 		}
 		prevEnd = end
 	}
 }

 type directiveInfo struct {
 	text   string // full text of the comment, not including newline
 	name   string // text after //go:
 	offset int    // byte offset of first slash in comment
 }

 func findDirectives(source []byte) []directiveInfo {
 	var directives []directiveInfo
 	directivePrefix := []byte("\n//go:")
 	offset := 0
 	for {
 		i := bytes.Index(source[offset:], directivePrefix)
 		if i < 0 {
 			break
 		}
 		i++ // skip newline
 		p := source[offset+i:]
 		j := bytes.IndexByte(p, '\n')
 		if j < 0 {
 			// reached EOF
 			j = len(p)
 		}
 		directive := directiveInfo{
 			text:   string(p[:j]),
 			name:   string(p[len(directivePrefix)-1 : j]),
 			offset: offset + i,
 		}
 		directives = append(directives, directive)
 		offset += i + j
 	}
 	return directives
 }

 // Makes sure that `cover -func=profile.cov` reports accurate coverage.
 // Issue #20515.
 func TestCoverFunc(t *testing.T) {
 	t.Parallel()
 	buildCover(t)
 	// testcover -func ./testdata/profile.cov
 	cmd := exec.Command(testcover, "-func", coverProfile)
 	out, err := cmd.Output()
 	if err != nil {
 		if ee, ok := err.(*exec.ExitError); ok {
 			t.Logf("%s", ee.Stderr)
 		}
 		t.Fatal(err)
 	}

 	if got, err := regexp.Match(".*total:.*100.0.*", out); err != nil || !got {
 		t.Logf("%s", out)
 		t.Errorf("invalid coverage counts. got=(%v, %v); want=(true; nil)", got, err)
 	}
 }

 // Check that cover produces correct HTML.
 // Issue #25767.
 func TestCoverHTML(t *testing.T) {
 	t.Parallel()
 	testenv.MustHaveGoRun(t)
 	buildCover(t)

 	// go test -coverprofile testdata/html/html.cov cmd/cover/testdata/html
 	cmd := exec.Command(testenv.GoToolPath(t), "test", toolexecArg, "-coverprofile", htmlProfile, "cmd/cover/testdata/html")
 	run(cmd, t)
 	// testcover -html testdata/html/html.cov -o testdata/html/html.html
 	cmd = exec.Command(testcover, "-html", htmlProfile, "-o", htmlHTML)
 	run(cmd, t)

 	// Extract the parts of the HTML with comment markers,
 	// and compare against a golden file.
 	entireHTML, err := os.ReadFile(htmlHTML)
 	if err != nil {
 		t.Fatal(err)
 	}
 	var out bytes.Buffer
 	scan := bufio.NewScanner(bytes.NewReader(entireHTML))
 	in := false
 	for scan.Scan() {
 		line := scan.Text()
 		if strings.Contains(line, "// START") {
 			in = true
 		}
 		if in {
 			fmt.Fprintln(&out, line)
 		}
 		if strings.Contains(line, "// END") {
 			in = false
 		}
 	}
 	if scan.Err() != nil {
 		t.Error(scan.Err())
 	}
 	golden, err := os.ReadFile(htmlGolden)
 	if err != nil {
 		t.Fatalf("reading golden file: %v", err)
 	}
 	// Ignore white space differences.
 	// Break into lines, then compare by breaking into words.
 	goldenLines := strings.Split(string(golden), "\n")
 	outLines := strings.Split(out.String(), "\n")
 	// Compare at the line level, stopping at first different line so
 	// we don't generate tons of output if there's an inserted or deleted line.
 	for i, goldenLine := range goldenLines {
 		if i >= len(outLines) {
 			t.Fatalf("output shorter than golden; stops before line %d: %s\n", i+1, goldenLine)
 		}
 		// Convert all white space to simple spaces, for easy comparison.
 		goldenLine = strings.Join(strings.Fields(goldenLine), " ")
 		outLine := strings.Join(strings.Fields(outLines[i]), " ")
 		if outLine != goldenLine {
 			t.Fatalf("line %d differs: got:\n\t%s\nwant:\n\t%s", i+1, outLine, goldenLine)
 		}
 	}
 	if len(goldenLines) != len(outLines) {
 		t.Fatalf("output longer than golden; first extra output line %d: %q\n", len(goldenLines)+1, outLines[len(goldenLines)])
 	}
 }

 // Test HTML processing with a source file not run through gofmt.
 // Issue #27350.
 func TestHtmlUnformatted(t *testing.T) {
 	t.Parallel()
 	testenv.MustHaveGoRun(t)
 	buildCover(t)

 	if err := os.Mkdir(htmlUDir, 0777); err != nil {
 		t.Fatal(err)
 	}

 	if err := os.WriteFile(filepath.Join(htmlUDir, "go.mod"), []byte("module htmlunformatted\n"), 0666); err != nil {
 		t.Fatal(err)
 	}

 	const htmlUContents = `
 package htmlunformatted

 var g int

 func F() {
 //line x.go:1
 	{ { F(); goto lab } }
 lab:
 }`

 	const htmlUTestContents = `package htmlunformatted`

 	if err := os.WriteFile(htmlU, []byte(htmlUContents), 0444); err != nil {
 		t.Fatal(err)
 	}
 	if err := os.WriteFile(htmlUTest, []byte(htmlUTestContents), 0444); err != nil {
 		t.Fatal(err)
 	}

 	// go test -covermode=count -coverprofile TMPDIR/htmlunformatted.cov
 	cmd := exec.Command(testenv.GoToolPath(t), "test", toolexecArg, "-covermode=count", "-coverprofile", htmlUProfile)
 	cmd.Dir = htmlUDir
 	run(cmd, t)

 	// testcover -html TMPDIR/htmlunformatted.cov -o unformatted.html
 	cmd = exec.Command(testcover, "-html", htmlUProfile, "-o", htmlUHTML)
 	cmd.Dir = htmlUDir
 	run(cmd, t)
 }

 // lineDupContents becomes linedup.go in TestFuncWithDuplicateLines.
 const lineDupContents = `
 package linedup

 var G int

 func LineDup(c int) {
 	for i := 0; i < c; i++ {
 //line ld.go:100
 		if i % 2 == 0 {
 			G++
 		}
 		if i % 3 == 0 {
 			G++; G++
 		}
 //line ld.go:100
 		if i % 4 == 0 {
 			G++; G++; G++
 		}
 		if i % 5 == 0 {
 			G++; G++; G++; G++
 		}
 	}
 }
 `

 // lineDupTestContents becomes linedup_test.go in TestFuncWithDuplicateLines.
 const lineDupTestContents = `
 package linedup

 import "testing"

 func TestLineDup(t *testing.T) {
 	LineDup(100)
 }
 `

 // Test -func with duplicate //line directives with different numbers
 // of statements.
 func TestFuncWithDuplicateLines(t *testing.T) {
 	t.Parallel()
 	testenv.MustHaveGoRun(t)
 	buildCover(t)

 	if err := os.Mkdir(lineDupDir, 0777); err != nil {
 		t.Fatal(err)
 	}

 	if err := os.WriteFile(filepath.Join(lineDupDir, "go.mod"), []byte("module linedup\n"), 0666); err != nil {
 		t.Fatal(err)
 	}
 	if err := os.WriteFile(lineDupGo, []byte(lineDupContents), 0444); err != nil {
 		t.Fatal(err)
 	}
 	if err := os.WriteFile(lineDupTestGo, []byte(lineDupTestContents), 0444); err != nil {
 		t.Fatal(err)
 	}

 	// go test -cover -covermode count -coverprofile TMPDIR/linedup.out
 	cmd := exec.Command(testenv.GoToolPath(t), "test", toolexecArg, "-cover", "-covermode", "count", "-coverprofile", lineDupProfile)
 	cmd.Dir = lineDupDir
 	run(cmd, t)

 	// testcover -func=TMPDIR/linedup.out
 	cmd = exec.Command(testcover, "-func", lineDupProfile)
 	cmd.Dir = lineDupDir
 	run(cmd, t)
 }

 func run(c *exec.Cmd, t *testing.T) {
 	t.Helper()
 	t.Log("running", c.Args)
 	out, err := c.CombinedOutput()
 	if len(out) > 0 {
 		t.Logf("%s", out)
 	}
 	if err != nil {
 		t.Fatal(err)
 	}
 }
	// Copyright 2013 The Go Authors. All rights reserved.
	// Use of this source code is governed by a BSD-style
	// license that can be found in the LICENSE file.

	package main_test

	import (
	"bufio"
	"bytes"
	"flag"
	"fmt"
	"go/ast"
	"go/parser"
	"go/token"
	"internal/testenv"
	"os"
	"os/exec"
	"path/filepath"
	"regexp"
	"strings"
	"sync"
	"testing"
	)

	const (
	// Data directory, also the package directory for the test.
	testdata = "testdata"
	)

	var (
	// Input files.
	testMain = filepath.Join(testdata, "main.go")
	testTest = filepath.Join(testdata, "test.go")
	coverProfile = filepath.Join(testdata, "profile.cov")
	toolexecSource = filepath.Join(testdata, "toolexec.go")

	// The HTML test files are in a separate directory
	// so they are a complete package.
	htmlGolden = filepath.Join(testdata, "html", "html.golden")

	// Temporary files.
	tmpTestMain string
	coverInput string
	coverOutput string
	htmlProfile string
	htmlHTML string
	htmlUDir string
	htmlU string
	htmlUTest string
	htmlUProfile string
	htmlUHTML string
	lineDupDir string
	lineDupGo string
	lineDupTestGo string
	lineDupProfile string
	)

	var (
	// testTempDir is a temporary directory created in TestMain.
	testTempDir string

	// testcover is a newly built version of the cover program.
	testcover string

	// toolexec is a program to use as the go tool's -toolexec argument.
	toolexec string

	// testcoverErr records an error building testcover or toolexec.
	testcoverErr error

	// testcoverOnce is used to build testcover once.
	testcoverOnce sync.Once

	// toolexecArg is the argument to pass to the go tool.
	toolexecArg string
	)

	var debug = flag.Bool("debug", false, "keep rewritten files for debugging")

	// We use TestMain to set up a temporary directory and remove it when
	// the tests are done.
	func TestMain(m *testing.M) {
	dir, err := os.MkdirTemp("", "go-testcover")
	if err != nil {
	fmt.Fprintln(os.Stderr, err)
	os.Exit(1)
	}
	os.Setenv("GOPATH", filepath.Join(dir, "_gopath"))

	testTempDir = dir

	tmpTestMain = filepath.Join(dir, "main.go")
	coverInput = filepath.Join(dir, "test_line.go")
	coverOutput = filepath.Join(dir, "test_cover.go")
	htmlProfile = filepath.Join(dir, "html.cov")
	htmlHTML = filepath.Join(dir, "html.html")
	htmlUDir = filepath.Join(dir, "htmlunformatted")
	htmlU = filepath.Join(htmlUDir, "htmlunformatted.go")
	htmlUTest = filepath.Join(htmlUDir, "htmlunformatted_test.go")
	htmlUProfile = filepath.Join(htmlUDir, "htmlunformatted.cov")
	htmlUHTML = filepath.Join(htmlUDir, "htmlunformatted.html")
	lineDupDir = filepath.Join(dir, "linedup")
	lineDupGo = filepath.Join(lineDupDir, "linedup.go")
	lineDupTestGo = filepath.Join(lineDupDir, "linedup_test.go")
	lineDupProfile = filepath.Join(lineDupDir, "linedup.out")

	status := m.Run()

	if !*debug {
	os.RemoveAll(dir)
	}

	os.Exit(status)
	}

	// buildCover builds a version of the cover program for testing.
	// This ensures that "go test cmd/cover" tests the current cmd/cover.
	func buildCover(t *testing.T) {
	t.Helper()
	testenv.MustHaveGoBuild(t)
	testcoverOnce.Do(func() {
	var wg sync.WaitGroup
	wg.Add(2)

	var err1, err2 error
	go func() {
	defer wg.Done()
	testcover = filepath.Join(testTempDir, "cover.exe")
	t.Logf("running [go build -o %s]", testcover)
	out, err := exec.Command(testenv.GoToolPath(t), "build", "-o", testcover).CombinedOutput()
	if len(out) > 0 {
	t.Logf("%s", out)
	}
	err1 = err
	}()

	go func() {
	defer wg.Done()
	toolexec = filepath.Join(testTempDir, "toolexec.exe")
	t.Logf("running [go -build -o %s %s]", toolexec, toolexecSource)
	out, err := exec.Command(testenv.GoToolPath(t), "build", "-o", toolexec, toolexecSource).CombinedOutput()
	if len(out) > 0 {
	t.Logf("%s", out)
	}
	err2 = err
	}()

	wg.Wait()

	testcoverErr = err1
	if err2 != nil && err1 == nil {
	testcoverErr = err2
	}

	toolexecArg = "-toolexec=" + toolexec + " " + testcover
	})
	if testcoverErr != nil {
	t.Fatal("failed to build testcover or toolexec program:", testcoverErr)
	}
	}

	// Run this shell script, but do it in Go so it can be run by "go test".
	//
	// replace the word LINE with the line number < testdata/test.go > testdata/test_line.go
	// go build -o testcover
	// testcover -mode=count -var=CoverTest -o ./testdata/test_cover.go testdata/test_line.go
	// go run ./testdata/main.go ./testdata/test.go
	//
	func TestCover(t *testing.T) {
	t.Parallel()
	testenv.MustHaveGoRun(t)
	buildCover(t)

	// Read in the test file (testTest) and write it, with LINEs specified, to coverInput.
	file, err := os.ReadFile(testTest)
	if err != nil {
	t.Fatal(err)
	}
	lines := bytes.Split(file, []byte("\n"))
	for i, line := range lines {
	lines[i] = bytes.ReplaceAll(line, []byte("LINE"), []byte(fmt.Sprint(i+1)))
	}

	// Add a function that is not gofmt'ed. This used to cause a crash.
	// We don't put it in test.go because then we would have to gofmt it.
	// Issue 23927.
	lines = append(lines, []byte("func unFormatted() {"),
	[]byte("\tif true {"),
	[]byte("\t}else{"),
	[]byte("\t}"),
	[]byte("}"))
	lines = append(lines, []byte("func unFormatted2(b bool) {if b{}else{}}"))

	if err := os.WriteFile(coverInput, bytes.Join(lines, []byte("\n")), 0666); err != nil {
	t.Fatal(err)
	}

	// testcover -mode=count -var=thisNameMustBeVeryLongToCauseOverflowOfCounterIncrementStatementOntoNextLineForTest -o ./testdata/test_cover.go testdata/test_line.go
	cmd := exec.Command(testcover, "-mode=count", "-var=thisNameMustBeVeryLongToCauseOverflowOfCounterIncrementStatementOntoNextLineForTest", "-o", coverOutput, coverInput)
	run(cmd, t)

	cmd = exec.Command(testcover, "-mode=set", "-var=Not_an-identifier", "-o", coverOutput, coverInput)
	err = cmd.Run()
	if err == nil {
	t.Error("Expected cover to fail with an error")
	}

	// Copy testmain to testTempDir, so that it is in the same directory
	// as coverOutput.
	b, err := os.ReadFile(testMain)
	if err != nil {
	t.Fatal(err)
	}
	if err := os.WriteFile(tmpTestMain, b, 0444); err != nil {
	t.Fatal(err)
	}

	// go run ./testdata/main.go ./testdata/test.go
	cmd = exec.Command(testenv.GoToolPath(t), "run", tmpTestMain, coverOutput)
	run(cmd, t)

	file, err = os.ReadFile(coverOutput)
	if err != nil {
	t.Fatal(err)
	}
	// compiler directive must appear right next to function declaration.
	if got, err := regexp.MatchString(".\n//go:nosplit\nfunc someFunction().", string(file)); err != nil \|\| !got {
	t.Error("misplaced compiler directive")
	}
	// "go:linkname" compiler directive should be present.
	if got, err := regexp.MatchString(`.go\:linkname some\_name some\_name.`, string(file)); err != nil \|\| !got {
	t.Error("'go:linkname' compiler directive not found")
	}

	// Other comments should be preserved too.
	c := ".// This comment didn't appear in generated go code."
	if got, err := regexp.MatchString(c, string(file)); err != nil \|\| !got {
	t.Errorf("non compiler directive comment %q not found", c)
	}
	}

	// TestDirectives checks that compiler directives are preserved and positioned
	// correctly. Directives that occur before top-level declarations should remain
	// above those declarations, even if they are not part of the block of
	// documentation comments.
	func TestDirectives(t *testing.T) {
	t.Parallel()
	buildCover(t)

	// Read the source file and find all the directives. We'll keep
	// track of whether each one has been seen in the output.
	testDirectives := filepath.Join(testdata, "directives.go")
	source, err := os.ReadFile(testDirectives)
	if err != nil {
	t.Fatal(err)
	}
	sourceDirectives := findDirectives(source)

	// testcover -mode=atomic ./testdata/directives.go
	cmd := exec.Command(testcover, "-mode=atomic", testDirectives)
	cmd.Stderr = os.Stderr
	output, err := cmd.Output()
	if err != nil {
	t.Fatal(err)
	}

	// Check that all directives are present in the output.
	outputDirectives := findDirectives(output)
	foundDirective := make(map[string]bool)
	for _, p := range sourceDirectives {
	foundDirective[p.name] = false
	}
	for _, p := range outputDirectives {
	if found, ok := foundDirective[p.name]; !ok {
	t.Errorf("unexpected directive in output: %s", p.text)
	} else if found {
	t.Errorf("directive found multiple times in output: %s", p.text)
	}
	foundDirective[p.name] = true
	}
	for name, found := range foundDirective {
	if !found {
	t.Errorf("missing directive: %s", name)
	}
	}

	// Check that directives that start with the name of top-level declarations
	// come before the beginning of the named declaration and after the end
	// of the previous declaration.
	fset := token.NewFileSet()
	astFile, err := parser.ParseFile(fset, testDirectives, output, 0)
	if err != nil {
	t.Fatal(err)
	}

	prevEnd := 0
	for _, decl := range astFile.Decls {
	var name string
	switch d := decl.(type) {
	case *ast.FuncDecl:
	name = d.Name.Name
	case *ast.GenDecl:
	if len(d.Specs) == 0 {
	// An empty group declaration. We still want to check that
	// directives can be associated with it, so we make up a name
	// to match directives in the test data.
	name = "_empty"
	} else if spec, ok := d.Specs[0].(*ast.TypeSpec); ok {
	name = spec.Name.Name
	}
	}
	pos := fset.Position(decl.Pos()).Offset
	end := fset.Position(decl.End()).Offset
	if name == "" {
	prevEnd = end
	continue
	}
	for _, p := range outputDirectives {
	if !strings.HasPrefix(p.name, name) {
	continue
	}
	if p.offset < prevEnd \|\| pos < p.offset {
	t.Errorf("directive %s does not appear before definition %s", p.text, name)
	}
	}
	prevEnd = end
	}
	}

	type directiveInfo struct {
	text string // full text of the comment, not including newline
	name string // text after //go:
	offset int // byte offset of first slash in comment
	}

	func findDirectives(source []byte) []directiveInfo {
	var directives []directiveInfo
	directivePrefix := []byte("\n//go:")
	offset := 0
	for {
	i := bytes.Index(source[offset:], directivePrefix)
	if i < 0 {
	break
	}
	i++ // skip newline
	p := source[offset+i:]
	j := bytes.IndexByte(p, '\n')
	if j < 0 {
	// reached EOF
	j = len(p)
	}
	directive := directiveInfo{
	text: string(p[:j]),
	name: string(p[len(directivePrefix)-1 : j]),
	offset: offset + i,
	}
	directives = append(directives, directive)
	offset += i + j
	}
	return directives
	}

	// Makes sure that `cover -func=profile.cov` reports accurate coverage.
	// Issue #20515.
	func TestCoverFunc(t *testing.T) {
	t.Parallel()
	buildCover(t)
	// testcover -func ./testdata/profile.cov
	cmd := exec.Command(testcover, "-func", coverProfile)
	out, err := cmd.Output()
	if err != nil {
	if ee, ok := err.(*exec.ExitError); ok {
	t.Logf("%s", ee.Stderr)
	}
	t.Fatal(err)
	}

	if got, err := regexp.Match(".total:.100.0.*", out); err != nil \|\| !got {
	t.Logf("%s", out)
	t.Errorf("invalid coverage counts. got=(%v, %v); want=(true; nil)", got, err)
	}
	}

	// Check that cover produces correct HTML.
	// Issue #25767.
	func TestCoverHTML(t *testing.T) {
	t.Parallel()
	testenv.MustHaveGoRun(t)
	buildCover(t)

	// go test -coverprofile testdata/html/html.cov cmd/cover/testdata/html
	cmd := exec.Command(testenv.GoToolPath(t), "test", toolexecArg, "-coverprofile", htmlProfile, "cmd/cover/testdata/html")
	run(cmd, t)
	// testcover -html testdata/html/html.cov -o testdata/html/html.html
	cmd = exec.Command(testcover, "-html", htmlProfile, "-o", htmlHTML)
	run(cmd, t)

	// Extract the parts of the HTML with comment markers,
	// and compare against a golden file.
	entireHTML, err := os.ReadFile(htmlHTML)
	if err != nil {
	t.Fatal(err)
	}
	var out bytes.Buffer
	scan := bufio.NewScanner(bytes.NewReader(entireHTML))
	in := false
	for scan.Scan() {
	line := scan.Text()
	if strings.Contains(line, "// START") {
	in = true
	}
	if in {
	fmt.Fprintln(&out, line)
	}
	if strings.Contains(line, "// END") {
	in = false
	}
	}
	if scan.Err() != nil {
	t.Error(scan.Err())
	}
	golden, err := os.ReadFile(htmlGolden)
	if err != nil {
	t.Fatalf("reading golden file: %v", err)
	}
	// Ignore white space differences.
	// Break into lines, then compare by breaking into words.
	goldenLines := strings.Split(string(golden), "\n")
	outLines := strings.Split(out.String(), "\n")
	// Compare at the line level, stopping at first different line so
	// we don't generate tons of output if there's an inserted or deleted line.
	for i, goldenLine := range goldenLines {
	if i >= len(outLines) {
	t.Fatalf("output shorter than golden; stops before line %d: %s\n", i+1, goldenLine)
	}
	// Convert all white space to simple spaces, for easy comparison.
	goldenLine = strings.Join(strings.Fields(goldenLine), " ")
	outLine := strings.Join(strings.Fields(outLines[i]), " ")
	if outLine != goldenLine {
	t.Fatalf("line %d differs: got:\n\t%s\nwant:\n\t%s", i+1, outLine, goldenLine)
	}
	}
	if len(goldenLines) != len(outLines) {
	t.Fatalf("output longer than golden; first extra output line %d: %q\n", len(goldenLines)+1, outLines[len(goldenLines)])
	}
	}

	// Test HTML processing with a source file not run through gofmt.
	// Issue #27350.
	func TestHtmlUnformatted(t *testing.T) {
	t.Parallel()
	testenv.MustHaveGoRun(t)
	buildCover(t)

	if err := os.Mkdir(htmlUDir, 0777); err != nil {
	t.Fatal(err)
	}

	if err := os.WriteFile(filepath.Join(htmlUDir, "go.mod"), []byte("module htmlunformatted\n"), 0666); err != nil {
	t.Fatal(err)
	}

	const htmlUContents = `
	package htmlunformatted

	var g int

	func F() {
	//line x.go:1
	{ { F(); goto lab } }
	lab:
	}`

	const htmlUTestContents = `package htmlunformatted`

	if err := os.WriteFile(htmlU, []byte(htmlUContents), 0444); err != nil {
	t.Fatal(err)
	}
	if err := os.WriteFile(htmlUTest, []byte(htmlUTestContents), 0444); err != nil {
	t.Fatal(err)
	}

	// go test -covermode=count -coverprofile TMPDIR/htmlunformatted.cov
	cmd := exec.Command(testenv.GoToolPath(t), "test", toolexecArg, "-covermode=count", "-coverprofile", htmlUProfile)
	cmd.Dir = htmlUDir
	run(cmd, t)

	// testcover -html TMPDIR/htmlunformatted.cov -o unformatted.html
	cmd = exec.Command(testcover, "-html", htmlUProfile, "-o", htmlUHTML)
	cmd.Dir = htmlUDir
	run(cmd, t)
	}

	// lineDupContents becomes linedup.go in TestFuncWithDuplicateLines.
	const lineDupContents = `
	package linedup

	var G int

	func LineDup(c int) {
	for i := 0; i < c; i++ {
	//line ld.go:100
	if i % 2 == 0 {
	G++
	}
	if i % 3 == 0 {
	G++; G++
	}
	//line ld.go:100
	if i % 4 == 0 {
	G++; G++; G++
	}
	if i % 5 == 0 {
	G++; G++; G++; G++
	}
	}
	}
	`

	// lineDupTestContents becomes linedup_test.go in TestFuncWithDuplicateLines.
	const lineDupTestContents = `
	package linedup

	import "testing"

	func TestLineDup(t *testing.T) {
	LineDup(100)
	}
	`

	// Test -func with duplicate //line directives with different numbers
	// of statements.
	func TestFuncWithDuplicateLines(t *testing.T) {
	t.Parallel()
	testenv.MustHaveGoRun(t)
	buildCover(t)

	if err := os.Mkdir(lineDupDir, 0777); err != nil {
	t.Fatal(err)
	}

	if err := os.WriteFile(filepath.Join(lineDupDir, "go.mod"), []byte("module linedup\n"), 0666); err != nil {
	t.Fatal(err)
	}
	if err := os.WriteFile(lineDupGo, []byte(lineDupContents), 0444); err != nil {
	t.Fatal(err)
	}
	if err := os.WriteFile(lineDupTestGo, []byte(lineDupTestContents), 0444); err != nil {
	t.Fatal(err)
	}

	// go test -cover -covermode count -coverprofile TMPDIR/linedup.out
	cmd := exec.Command(testenv.GoToolPath(t), "test", toolexecArg, "-cover", "-covermode", "count", "-coverprofile", lineDupProfile)
	cmd.Dir = lineDupDir
	run(cmd, t)

	// testcover -func=TMPDIR/linedup.out
	cmd = exec.Command(testcover, "-func", lineDupProfile)
	cmd.Dir = lineDupDir
	run(cmd, t)
	}

	func run(c exec.Cmd, t testing.T) {
	t.Helper()
	t.Log("running", c.Args)
	out, err := c.CombinedOutput()
	if len(out) > 0 {
	t.Logf("%s", out)
	}
	if err != nil {
	t.Fatal(err)
	}
	}