diff --git a/src/infra/backoff.test.ts b/src/infra/backoff.test.ts
new file mode 100644
index 00000000000..9181d832402
--- /dev/null
+++ b/src/infra/backoff.test.ts
@@ -0,0 +1,36 @@
+import { describe, expect, it, vi } from "vitest";
+import { computeBackoff, sleepWithAbort, type BackoffPolicy } from "./backoff.js";
+
+describe("backoff helpers", () => {
+  const policy: BackoffPolicy = {
+    initialMs: 100,
+    maxMs: 250,
+    factor: 2,
+    jitter: 0.5,
+  };
+
+  it("treats attempts below one as the first backoff step", () => {
+    const randomSpy = vi.spyOn(Math, "random").mockReturnValue(0);
+    try {
+      expect(computeBackoff(policy, 0)).toBe(100);
+      expect(computeBackoff(policy, 1)).toBe(100);
+    } finally {
+      randomSpy.mockRestore();
+    }
+  });
+
+  it("adds jitter and clamps to maxMs", () => {
+    const randomSpy = vi.spyOn(Math, "random").mockReturnValue(1);
+    try {
+      expect(computeBackoff(policy, 2)).toBe(250);
+      expect(computeBackoff({ ...policy, maxMs: 450 }, 2)).toBe(300);
+    } finally {
+      randomSpy.mockRestore();
+    }
+  });
+
+  it("returns immediately for non-positive sleep durations", async () => {
+    await expect(sleepWithAbort(0, AbortSignal.abort())).resolves.toBeUndefined();
+    await expect(sleepWithAbort(-5)).resolves.toBeUndefined();
+  });
+});
diff --git a/src/infra/system-run-normalize.test.ts b/src/infra/system-run-normalize.test.ts
new file mode 100644
index 00000000000..6bf2f56d4e9
--- /dev/null
+++ b/src/infra/system-run-normalize.test.ts
@@ -0,0 +1,17 @@
+import { describe, expect, it } from "vitest";
+import { normalizeNonEmptyString, normalizeStringArray } from "./system-run-normalize.js";
+
+describe("system run normalization helpers", () => {
+  it("normalizes only non-empty trimmed strings", () => {
+    expect(normalizeNonEmptyString("  hello  ")).toBe("hello");
+    expect(normalizeNonEmptyString(" \n\t ")).toBeNull();
+    expect(normalizeNonEmptyString(42)).toBeNull();
+    expect(normalizeNonEmptyString(null)).toBeNull();
+  });
+
+  it("normalizes array entries and rejects non-arrays", () => {
+    expect(normalizeStringArray([" alpha ", 42, false])).toEqual([" alpha ", "42", "false"]);
+    expect(normalizeStringArray(undefined)).toEqual([]);
+    expect(normalizeStringArray("alpha")).toEqual([]);
+  });
+});