Function TestApplyReportsRestoreFailure

internal/update/update_test.go:154–181

TestApplyReportsRestoreFailure covers the doubly-bad path: the promote rename fails AND the restore of the moved-aside binary also fails. Apply must surface the restore failure (not just the promote one) so the message reflects reality: execPath is now empty. Forced by occupying execPath with a dire

(t *testing.T)

// reflects reality: execPath is now empty. Forced by occupying execPath with
// a directory inside the seam, so the restore os.Rename hits EISDIR.
func TestApplyReportsRestoreFailure(t *testing.T) {
	asset := platformAsset(t)
	body := []byte("verified new binary\n")
	r := newFakeRelease(t, asset, body, hashOf(body))
	withReleaseURLs(t, r.srv.URL)

	tmpDir := t.TempDir()
	exec := filepath.Join(tmpDir, "codehamr")
	if err := os.WriteFile(exec, []byte("the original running binary\n"), 0o755); err != nil {
		t.Fatal(err)
	}

	orig := promoteRename
	// Occupy the now-vacant execPath with a directory so the restore can't succeed.
	promoteRename = func(_, to string) error {
		_ = os.Mkdir(to, 0o755)
		return fmt.Errorf("simulated promote failure")
	}
	t.Cleanup(func() { promoteRename = orig })

	err := Apply(context.Background(), exec)
	if err == nil {
		t.Fatal("Apply must surface the failure")
	}
	if !strings.Contains(err.Error(), "restore") {
		t.Fatalf("error must name the restore failure (binary may be missing), got: %v", err)
	}
}

// TestApplyAcceptsMatchingChecksum: positive case, a download whose hash
// equals the manifest entry promotes the binary into place.