cmd/cover: remove use of diff in cover_test.go

It's non-portable, and the test isn't hard to write without diff.
It still produces helpful output in case of trouble:

--- FAIL: TestCoverHTML (0.75s)
    cover_test.go:325: line 4 differs: got:
        	case &lt;-ch:<span class="cov0" title="0"></span>
        want:
        	case &lt;-ch:<span class="cov0" xitle="0"></span>

This makes the test operating-system independent.

Change-Id: Iff35f00cb76ba89bc1b93db01c6f994e74341f4a
Reviewed-on: https://go-review.googlesource.com/118795
Reviewed-by: Ian Lance Taylor <iant@golang.org>
Run-TryBot: Ian Lance Taylor <iant@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>

diff --git a/src/cmd/cover/cover_test.go b/src/cmd/cover/cover_test.go
index ec80f94e59d93333c2096ad3c786d453ca2dba15..23a609996bbea1691ccd3b72951f529c56832073 100644 (file)
--- a/src/cmd/cover/cover_test.go
+++ b/src/cmd/cover/cover_test.go
@@ -18,7 +18,6 @@ import (
        "os/exec"
        "path/filepath"
        "regexp"
-       "runtime"
        "strings"
        "testing"
 )
@@ -267,9 +266,6 @@ func TestCoverFunc(t *testing.T) {
 // Check that cover produces correct HTML.
 // Issue #25767.
 func TestCoverHTML(t *testing.T) {
-       if _, err := exec.LookPath("diff"); err != nil {
-               t.Skipf("skip test on %s: diff command is required", runtime.GOOS)
-       }
        testenv.MustHaveGoBuild(t)
        if !*debug {
                defer os.Remove(testcover)
@@ -307,16 +303,30 @@ func TestCoverHTML(t *testing.T) {
                        in = false
                }
        }
-       if err := ioutil.WriteFile(htmlHTML, out.Bytes(), 0644); err != nil {
-               t.Fatal(err)
+       golden, err := ioutil.ReadFile(htmlGolden)
+       if err != nil {
+               t.Fatalf("reading golden file: %v", err)
        }
-       diff := "diff"
-       if runtime.GOOS == "plan9" {
-               diff = "/bin/ape/diff"
+       // 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), outLines[len(goldenLines)])
        }
-       // diff -uw testdata/html/html.html testdata/html/html.golden
-       cmd = exec.Command(diff, "-u", "-w", htmlHTML, htmlGolden)
-       run(cmd, t)
 }
 
 func run(c *exec.Cmd, t *testing.T) {