Add ior crash/timeout harness tests (task 343)

- Add waitBoth unit tests: ior exit error, ior timeout, both timeout,
  both succeed — using real processes (true/false/sleep)
- Add TestIorCrashReportsError: full harness test with fake ior binary
  that exits with error, verifying error mentions 'ior' and workload PID
  is returned
- Add TestIorStartFailureCleansUpWorkload: verifies workload process is
  killed when ior binary doesn't exist, checking with signal 0
- Refactor waitBoth to accept grace duration parameter for testability
  (production code passes iorShutdownGrace, tests use 500ms)
- Fix pipe drain in startWorkload: drain remaining stdout after reading
  PID so cmd.Wait() doesn't block on pending I/O
- Add writeScript helper to helpers_test.go for creating fake binaries

Co-authored-by: Amp <amp@ampcode.com>
Amp-Thread-ID: https://ampcode.com/threads/T-019c8162-c1cf-7612-b8f5-84c61e3d2021

1 files changed, 10 insertions, 0 deletions

diff --git a/integrationtests/helpers_test.go b/integrationtests/helpers_test.go
index edf57b9..7db54b2 100644
--- a/integrationtests/helpers_test.go
+++ b/integrationtests/helpers_test.go
@@ -36,6 +36,16 @@ func absPath(t *testing.T, rel string) string {
 	return p
 }
 
+// writeScript creates an executable shell script in dir and returns its path.
+func writeScript(t *testing.T, dir, name, content string) string {
+	t.Helper()
+	path := filepath.Join(dir, name)
+	if err := os.WriteFile(path, []byte("#!/bin/sh\n"+content+"\n"), 0o755); err != nil {
+		t.Fatalf("write script %s: %v", name, err)
+	}
+	return path
+}
+
 func runScenario(t *testing.T, scenario string, expected []ExpectedEvent) {
 	t.Helper()
 	h := newTestHarness(t)