Scanner status tests no longer depend on a 100 ms timer (closes #124)

The two status-send tests now call the send directly on a channel nobody
receives from, so a blocking send hangs the test into its timeout instead
of racing a 100 ms timer that a loaded host can miss.

The gpg test for a child holding gpg's output had the same problem: its
100 ms deadline could fire before the fake gpg wrote the PID of sleep,
and the cleanup then failed. The fake gpg now writes that PID to a named
pipe, and the test cancels only after reading it. It then waits up to
10 s for the call, so a call that waits for sleep fails the test and the
cleanup still kills sleep.

Model: opus-5-5

Dockerfile

@@ -67,7 +67,10 @@ RUN version="${VERSION:-$(git describe --tags --always)}"; \
         exit 1; \
     fi; \
     cd cmd/mfer && \
-    go build -tags urfave_cli_no_docs -ldflags "-X main.Gitrev=$version" -o /mfer .
+    CGO_ENABLED=0 go build -tags urfave_cli_no_docs -ldflags "-X main.Gitrev=$version" -o /mfer .
+
+# Fail unless /mfer is statically linked: scratch has no C library to run it.
+RUN ldd /mfer 2>&1 | grep -q 'not a dynamic executable'
 
 FROM scratch
 COPY --from=builder /mfer /mfer

mfer/gpg_test.go

@@ -10,6 +10,7 @@ import (
 	"path/filepath"
 	"strconv"
 	"strings"
+	"syscall"
 	"testing"
 	"time"
 
@@ -425,36 +426,51 @@ func TestGPGTimeoutKillsGPG(t *testing.T) {
 	assert.Contains(t, err.Error(), "gpg sign failed: gpg timed out")
 }
 
-// TestGPGTimeoutWhenChildHoldsOutput uses a fake gpg that runs sleep as a
+// TestGPGCancelWhenChildHoldsOutput uses a fake gpg that runs sleep as a
 // child instead of exec-ing it, the way a wrapper script around the real
 // gpg might. Killing the fake gpg leaves sleep holding its stdout and
-// stderr open; the call must still return shortly after the deadline
-// instead of waiting for sleep to exit. The fake gpg writes the process ID
-// of sleep to a file so that the test can kill it before returning.
-func TestGPGTimeoutWhenChildHoldsOutput(t *testing.T) {
-	pidFile := filepath.Join(t.TempDir(), "sleep.pid")
+// stderr open; the call must still return once ctx ends instead of waiting
+// for sleep to exit. The fake gpg writes the process ID of sleep to a named
+// pipe; the test ends ctx only after reading it, so sleep is running by
+// then, and kills sleep before returning.
+func TestGPGCancelWhenChildHoldsOutput(t *testing.T) {
+	pidPipe := filepath.Join(t.TempDir(), "sleep.pid")
+	require.NoError(t, syscall.Mkfifo(pidPipe, 0o600))
+	// sleep outlasts the 10 s wait below, so a call that waits for it fails.
 	t.Setenv("PATH", fakeGPGPath(t,
-		"#!/bin/sh\nsleep 3 &\necho $! >'"+pidFile+"'\nwait\n"))
-	t.Cleanup(func() {
-		pid, err := os.ReadFile(pidFile) //nolint:gosec // G304: path inside t.TempDir()
-		require.NoError(t, err)
+		"#!/bin/sh\nsleep 60 &\necho $! >'"+pidPipe+"'\nwait\n"))
 
-		n, err := strconv.Atoi(strings.TrimSpace(string(pid)))
-		require.NoError(t, err)
-
-		sleep, err := os.FindProcess(n)
-		require.NoError(t, err)
-		require.NoError(t, sleep.Kill())
-	})
-
-	ctx, cancel := context.WithTimeout(context.Background(), 100*time.Millisecond)
+	ctx, cancel := context.WithCancel(context.Background())
 	defer cancel()
 
-	start := time.Now()
-	_, err := gpgSign(ctx, []byte("data"), GPGKeyID("any"))
-	require.ErrorIs(t, err, context.DeadlineExceeded)
-	assert.Less(t, time.Since(start), 3*time.Second,
-		"the call waited for the child holding gpg's output to exit")
+	signErr := make(chan error, 1)
+
+	go func() {
+		_, err := gpgSign(ctx, []byte("data"), GPGKeyID("any"))
+		signErr <- err
+	}()
+
+	pid, err := os.ReadFile(pidPipe) //nolint:gosec // G304: path inside t.TempDir()
+	require.NoError(t, err)
+
+	n, err := strconv.Atoi(strings.TrimSpace(string(pid)))
+	require.NoError(t, err)
+
+	sleep, err := os.FindProcess(n)
+	require.NoError(t, err)
+	t.Cleanup(func() { require.NoError(t, sleep.Kill()) })
+
+	cancel()
+
+	// The call should return about gpgWaitDelay (one second) after the
+	// cancel. 10 s is far above that and well under the 30 s test timeout,
+	// which would abort the whole package before the cleanup kills sleep.
+	select {
+	case err := <-signErr:
+		require.ErrorIs(t, err, context.Canceled)
+	case <-time.After(10 * time.Second):
+		t.Fatal("the call waited for the child holding gpg's output to exit")
+	}
 }
 
 // TestBuildPassesContextToSigning checks that a caller can cancel the gpg

mfer/scanner_test.go

@@ -304,46 +304,19 @@ func TestScannerEnumerateFS(t *testing.T) {
 func TestSendEnumerateStatusNonBlocking(t *testing.T) {
 	t.Parallel()
 
-	// Channel with no buffer - send should not block
+	// Nobody receives, so a blocking send would hang the test into its timeout.
 	ch := make(chan EnumerateStatus)
 
-	// This should not block
-	done := make(chan bool)
-
-	go func() {
-		sendEnumerateStatus(ch, EnumerateStatus{FilesFound: 1})
-
-		done <- true
-	}()
-
-	select {
-	case <-done:
-		// Success - did not block
-	case <-time.After(100 * time.Millisecond):
-		t.Fatal("sendEnumerateStatus blocked on full channel")
-	}
+	sendEnumerateStatus(ch, EnumerateStatus{FilesFound: 1})
 }
 
 func TestSendScanStatusNonBlocking(t *testing.T) {
 	t.Parallel()
 
-	// Channel with no buffer - send should not block
+	// Nobody receives, so a blocking send would hang the test into its timeout.
 	ch := make(chan ScanStatus)
 
-	done := make(chan bool)
-
-	go func() {
-		sendScanStatus(ch, ScanStatus{ScannedFiles: 1})
-
-		done <- true
-	}()
-
-	select {
-	case <-done:
-		// Success - did not block
-	case <-time.After(100 * time.Millisecond):
-		t.Fatal("sendScanStatus blocked on full channel")
-	}
+	sendScanStatus(ch, ScanStatus{ScannedFiles: 1})
 }
 
 func TestSendStatusNilChannel(t *testing.T) {