1 files changed, 56 insertions, 0 deletions
diff --git a/gui/internal/model/preview_test.go b/gui/internal/model/preview_test.go
index 8c19922..b620a92 100644
--- a/gui/internal/model/preview_test.go
+++ b/gui/internal/model/preview_test.go
@@ -5,6 +5,7 @@ package model
 import (
 	"context"
 	"os"
+	"os/exec"
 	"path/filepath"
 	"strings"
 	"testing"
@@ -96,3 +97,58 @@ func TestPreviewShowsOnlyTheHead(t *testing.T) {
 		t.Error("a cut file does not say it was cut")
 	}
 }
+
+// TestPdfPreviewsDoNotMixUp: two PDFs looked at one after the other each
+// get their own rendered page. pdftoppm names its file after the page
+// number, so previews sharing a directory would collide - one of his ended
+// up showing another document's cover.
+func TestPdfPreviewsDoNotMixUp(t *testing.T) {
+	if _, err := exec.LookPath("pdftoppm"); err != nil {
+		t.Skip("pdftoppm is not installed")
+	}
+	if _, err := exec.LookPath("groff"); err != nil {
+		t.Skip("groff is not installed, so there is nothing to make a PDF with")
+	}
+	dir := t.TempDir()
+	pdf := func(name, text string) string {
+		p := filepath.Join(dir, name)
+		f, err := os.Create(p)
+		if err != nil {
+			t.Fatal(err)
+		}
+		defer f.Close()
+		cmd := exec.Command("groff", "-Tpdf", "-ms")
+		cmd.Stdin = strings.NewReader(".TL\n" + text + "\n")
+		cmd.Stdout = f
+		if err := cmd.Run(); err != nil {
+			t.Skipf("groff cannot write a PDF here: %v", err)
+		}
+		return p
+	}
+	first := pdf("first.pdf", "The first document")
+	second := pdf("second.pdf", "The second document")
+
+	tmp := t.TempDir()
+	a := MakePreview(context.Background(), first, tmp)
+	b := MakePreview(context.Background(), second, tmp)
+	if a.Kind != PreviewImage || b.Kind != PreviewImage {
+		t.Fatalf("previews = %+v, %+v", a, b)
+	}
+	if a.Image == b.Image {
+		t.Fatalf("both previews point at %s", a.Image)
+	}
+	sameBytes := func(x, y string) bool {
+		bx, err1 := os.ReadFile(x)
+		by, err2 := os.ReadFile(y)
+		return err1 == nil && err2 == nil && string(bx) == string(by)
+	}
+	if sameBytes(a.Image, b.Image) {
+		t.Error("the second preview is a copy of the first page rendered")
+	}
+	// The caller is told where to clean up.
+	for _, p := range []Preview{a, b} {
+		if p.Dir == "" {
+			t.Error("a rendered page comes with no directory to remove")
+		}
+	}
+}