1 files changed, 135 insertions, 0 deletions
diff --git a/src/cmd/fix/main_test.go b/src/cmd/fix/main_test.go
new file mode 100644
index 0000000..af16bca
--- /dev/null
+++ b/src/cmd/fix/main_test.go
@@ -0,0 +1,135 @@
+// Copyright 2011 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
+
+import (
+	"go/ast"
+	"go/parser"
+	"strings"
+	"testing"
+
+	"cmd/internal/diff"
+)
+
+type testCase struct {
+	Name string
+	Fn   func(*ast.File) bool
+	In   string
+	Out  string
+}
+
+var testCases []testCase
+
+func addTestCases(t []testCase, fn func(*ast.File) bool) {
+	// Fill in fn to avoid repetition in definitions.
+	if fn != nil {
+		for i := range t {
+			if t[i].Fn == nil {
+				t[i].Fn = fn
+			}
+		}
+	}
+	testCases = append(testCases, t...)
+}
+
+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("parsing: %v", err)
+		return
+	}
+
+	outb, err := gofmtFile(file)
+	if err != nil {
+		t.Errorf("printing: %v", err)
+		return
+	}
+	if s := string(outb); in != s && mustBeGofmt {
+		t.Errorf("not gofmt-formatted.\n--- %s\n%s\n--- %s | gofmt\n%s",
+			desc, in, desc, s)
+		tdiff(t, in, s)
+		return
+	}
+
+	if fn == nil {
+		for _, fix := range fixes {
+			if fix.f(file) {
+				fixed = true
+			}
+		}
+	} else {
+		fixed = fn(file)
+	}
+
+	outb, err = gofmtFile(file)
+	if err != nil {
+		t.Errorf("printing: %v", err)
+		return
+	}
+
+	return string(outb), fixed, true
+}
+
+func TestRewrite(t *testing.T) {
+	for _, tt := range testCases {
+		tt := tt
+		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 {
+				return
+			}
+
+			// reformat to get printing right
+			out, _, ok = parseFixPrint(t, fnop, tt.Name, out, false)
+			if !ok {
+				return
+			}
+
+			if out != tt.Out {
+				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)
+				return
+			}
+
+			if changed := out != tt.In; changed != fixed {
+				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 {
+				return
+			}
+
+			if fixed2 {
+				t.Errorf("applied fixes during second round")
+				return
+			}
+
+			if out2 != out {
+				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)
+			}
+		})
+	}
+}
+
+func tdiff(t *testing.T, a, b string) {
+	data, err := diff.Diff("go-fix-test", []byte(a), []byte(b))
+	if err != nil {
+		t.Error(err)
+		return
+	}
+	t.Error(string(data))
+}