Add integration test framework: plan, workload binary, harness scaffolding

- INTEGRATIONTESTS-PLAN.md: full design for e2e integration tests
- integrationtests/cmd/ioworkload: standalone binary with 13 I/O scenarios
- integrationtests/expectations.go: ExpectedEvent type and assertion helpers
- integrationtests/parse.go: .ior.zst parser producing TestResult
- Export IterRecord and LoadFromFile in flamegraph package
- Fix TraceId -> TraceID, StringByName returns error instead of panic

Amp-Thread-ID: https://ampcode.com/threads/T-019c8031-c106-757a-95a0-7a5457163ce7
Co-authored-by: Amp <amp@ampcode.com>

1 files changed, 46 insertions, 0 deletions

diff --git a/integrationtests/cmd/ioworkload/main.go b/integrationtests/cmd/ioworkload/main.go
new file mode 100644
index 0000000..3ed9cb2
--- /dev/null
+++ b/integrationtests/cmd/ioworkload/main.go
@@ -0,0 +1,46 @@
+// ioworkload is a standalone binary that performs deterministic I/O operations
+// for integration testing of ior. It prints its PID to stdout, sleeps to allow
+// ior to attach BPF tracepoints, then executes the requested I/O scenario.
+package main
+
+import (
+	"flag"
+	"fmt"
+	"os"
+	"slices"
+	"time"
+)
+
+const startupDelay = 2 * time.Second
+
+func main() {
+	scenario := flag.String("scenario", "", "I/O scenario to execute")
+	flag.Parse()
+
+	if *scenario == "" {
+		fmt.Fprintln(os.Stderr, "usage: ioworkload --scenario=<name>")
+		os.Exit(2)
+	}
+
+	run, ok := scenarios[*scenario]
+	if !ok {
+		fmt.Fprintf(os.Stderr, "unknown scenario: %s\navailable scenarios:\n", *scenario)
+		var names []string
+		for name := range scenarios {
+			names = append(names, name)
+		}
+		slices.Sort(names)
+		for _, name := range names {
+			fmt.Fprintf(os.Stderr, "  %s\n", name)
+		}
+		os.Exit(2)
+	}
+
+	fmt.Println(os.Getpid())
+	time.Sleep(startupDelay)
+
+	if err := run(); err != nil {
+		fmt.Fprintf(os.Stderr, "scenario %s failed: %v\n", *scenario, err)
+		os.Exit(1)
+	}
+}