117 lines
2.9 KiB
Go
117 lines
2.9 KiB
Go
// Package snaptest compares rendered views with the PNG goldens in testdata/snapshots.
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package snaptest
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import (
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"bytes"
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"flag"
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"image"
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"image/png"
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"os"
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"os/exec"
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"path/filepath"
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"regexp"
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"runtime"
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"strings"
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"sync"
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"testing"
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"github.com/egoist/mygo/ui"
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)
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var update = flag.Bool("update", false, "rewrite snapshots")
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// Modes names the two themes a snapshot covers, in capture order.
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var Modes = []string{"light", "dark"}
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// child marks a process that renders snapshots itself.
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const child = "MUJICA_SNAPSHOT_CHILD"
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var ran sync.Map
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// dir is the module's testdata/snapshots/<os>, whatever package runs the test.
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var dir = func() string {
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_, file, _, ok := runtime.Caller(0)
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if !ok {
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panic("snaptest: no caller")
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}
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return filepath.Join(filepath.Dir(file), "..", "..", "testdata", "snapshots", runtime.GOOS)
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}()
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// Run compares view, themed by theme for each of Modes, with testdata/snapshots/<os>/<name>-<mode>.png.
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// drive, when non-nil, sends input before the capture.
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func Run(t *testing.T, name string, w, h int, theme func(c *ui.Context, mode string), view func(c *ui.Context), drive func(tt *ui.Tester)) {
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t.Helper()
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if os.Getenv(child) == "" {
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inChild(t)
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return
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}
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for _, m := range Modes {
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ready := false
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tt := ui.NewTester(func(c *ui.Context) {
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theme(c, m)
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if ready {
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view(c)
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}
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}, w, h)
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// Animations must not paint before ReduceMotion applies.
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tt.SetPreferences(ui.Preferences{ReduceMotion: true, TextScale: 1})
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ready = true
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tt.Frame()
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if drive != nil {
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drive(tt)
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}
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got := Encode(t, tt.Image())
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path := filepath.Join(dir, name+"-"+m+".png")
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if *update {
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if err := os.MkdirAll(filepath.Dir(path), 0o755); err != nil {
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t.Fatal(err)
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}
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if err := os.WriteFile(path, got, 0o644); err != nil {
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t.Fatal(err)
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}
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continue
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}
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want, err := os.ReadFile(path)
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if err != nil {
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t.Fatalf("%v (run go test -update)", err)
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}
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if !bytes.Equal(got, want) {
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if err := os.WriteFile(path+".got.png", got, 0o644); err != nil {
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t.Fatal(err)
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}
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t.Errorf("%s differs; see %s.got.png", path, path)
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}
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}
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}
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// inChild reruns the test alone in a fresh process; MyGo's path cache is process-wide.
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func inChild(t *testing.T) {
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t.Helper()
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if _, done := ran.LoadOrStore(t.Name(), true); done {
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return
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}
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parts := strings.Split(t.Name(), "/")
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for i, p := range parts {
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parts[i] = "^" + regexp.QuoteMeta(p) + "$"
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}
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args := []string{"-test.run=" + strings.Join(parts, "/"), "-test.count=1"}
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if *update {
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args = append(args, "-update")
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}
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cmd := exec.Command(os.Args[0], args...)
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cmd.Env = append(os.Environ(), child+"=1")
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if out, err := cmd.CombinedOutput(); err != nil {
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t.Fatalf("snapshot child failed: %v\n%s", err, out)
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}
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}
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// Encode returns img as PNG bytes.
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func Encode(t *testing.T, img image.Image) []byte {
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t.Helper()
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var b bytes.Buffer
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if err := png.Encode(&b, img); err != nil {
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t.Fatal(err)
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}
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return b.Bytes()
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}
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