cmd/fix: mark tests as parallel

This speeds up

go test -short -count=1 cmd/fix

on my machine from about 8s to about 0.05s.

Updates #26473

Change-Id: I698ee20704ae0aee874ba642e7b0e070ddc99194
Reviewed-on: https://go-review.googlesource.com/c/go/+/176900
Run-TryBot: Josh Bleecher Snyder <josharian@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

src/cmd/fix/main_test.go

@@ -37,18 +37,18 @@ func fnop(*ast.File) bool { return false }
 func parseFixPrint(t *testing.T, fn func(*ast.File) bool, desc, in string, mustBeGofmt bool) (out string, fixed, ok bool) {
 	file, err := parser.ParseFile(fset, desc, in, parserMode)
 	if err != nil {
-		t.Errorf("%s: parsing: %v", desc, err)
+		t.Errorf("parsing: %v", err)
 		return
 	}
 
 	outb, err := gofmtFile(file)
 	if err != nil {
-		t.Errorf("%s: printing: %v", desc, err)
+		t.Errorf("printing: %v", err)
 		return
 	}
 	if s := string(outb); in != s && mustBeGofmt {
-		t.Errorf("%s: not gofmt-formatted.\n--- %s\n%s\n--- %s | gofmt\n%s",
-			desc, desc, in, desc, s)
+		t.Errorf("not gofmt-formatted.\n--- %s\n%s\n--- %s | gofmt\n%s",
+			desc, in, desc, s)
 		tdiff(t, in, s)
 		return
 	}
@@ -65,7 +65,7 @@ func parseFixPrint(t *testing.T, fn func(*ast.File) bool, desc, in string, mustB
 
 	outb, err = gofmtFile(file)
 	if err != nil {
-		t.Errorf("%s: printing: %v", desc, err)
+		t.Errorf("printing: %v", err)
 		return
 	}
 
@@ -74,48 +74,51 @@ func parseFixPrint(t *testing.T, fn func(*ast.File) bool, desc, in string, mustB
 
 func TestRewrite(t *testing.T) {
 	for _, tt := range testCases {
+		t.Run(tt.Name, func(t *testing.T) {
+			t.Parallel()
 			// Apply fix: should get tt.Out.
 			out, fixed, ok := parseFixPrint(t, tt.Fn, tt.Name, tt.In, true)
 			if !ok {
-			continue
+				return
 			}
 
 			// reformat to get printing right
 			out, _, ok = parseFixPrint(t, fnop, tt.Name, out, false)
 			if !ok {
-			continue
+				return
 			}
 
 			if out != tt.Out {
-			t.Errorf("%s: incorrect output.\n", tt.Name)
+				t.Errorf("incorrect output.\n")
 				if !strings.HasPrefix(tt.Name, "testdata/") {
 					t.Errorf("--- have\n%s\n--- want\n%s", out, tt.Out)
 				}
 				tdiff(t, out, tt.Out)
-			continue
+				return
 			}
 
 			if changed := out != tt.In; changed != fixed {
-			t.Errorf("%s: changed=%v != fixed=%v", tt.Name, changed, fixed)
-			continue
+				t.Errorf("changed=%v != fixed=%v", changed, fixed)
+				return
 			}
 
 			// Should not change if run again.
 			out2, fixed2, ok := parseFixPrint(t, tt.Fn, tt.Name+" output", out, true)
 			if !ok {
-			continue
+				return
 			}
 
 			if fixed2 {
-			t.Errorf("%s: applied fixes during second round", tt.Name)
-			continue
+				t.Errorf("applied fixes during second round")
+				return
 			}
 
 			if out2 != out {
-			t.Errorf("%s: changed output after second round of fixes.\n--- output after first round\n%s\n--- output after second round\n%s",
-				tt.Name, out, out2)
+				t.Errorf("changed output after second round of fixes.\n--- output after first round\n%s\n--- output after second round\n%s",
+					out, out2)
 				tdiff(t, out, out2)
 			}
+		})
 	}
 }