Redact and cap subprocess diagnostics

internal/adapters/subprocess/process_tree_supported_test.go

@@ -7,6 +7,7 @@ import (
 	"errors"
 	"os"
 	"path/filepath"
+	"strings"
 	"testing"
 	"time"
 )
@@ -49,6 +50,30 @@ func TestRunTimeoutTerminatesProcessTree(t *testing.T) {
 	assertDescendantDidNotSurvive(t, sentinelPath)
 }
 
+func TestRunCaptureLimitTerminatesProcessTree(t *testing.T) {
+	req, sentinelPath := processTreeRequest(t)
+	req.Args[len(req.Args)-1] = "tree-spam"
+
+	result, err := Run(context.Background(), req)
+	if err == nil {
+		t.Fatal("Run() error = nil, want capture-limit error")
+	}
+	if result.ExitCode == 0 {
+		t.Fatalf("ExitCode = %d, want terminated process", result.ExitCode)
+	}
+	if !strings.Contains(err.Error(), "stdout diagnostic capture for subprocess exceeded") {
+		t.Fatalf("error = %q, want stdout capture-limit context", err)
+	}
+	info, statErr := os.Stat(req.StdoutLogPath)
+	if statErr != nil {
+		t.Fatalf("stat stdout diagnostic: %v", statErr)
+	}
+	if info.Size() != MaxStdoutDiagnosticBytes {
+		t.Fatalf("stdout diagnostic size = %d, want %d", info.Size(), MaxStdoutDiagnosticBytes)
+	}
+	assertDescendantDidNotSurvive(t, sentinelPath)
+}
+
 type runOutcome struct {
 	result RunResult
 	err    error