diff --git a/__tests__/cache.test.ts b/__tests__/cache.test.ts
index eaa0192..d167432 100644
--- a/__tests__/cache.test.ts
+++ b/__tests__/cache.test.ts
@@ -111,6 +111,22 @@ describe("sdkCachePath", () => {
 			process.env.RUNNER_TOOL_CACHE = original;
 		}
 	});
+
+	// On a runner RUNNER_TOOL_CACHE is always set, so the fallback is only
+	// reached when this test clears it.
+	it("falls back to the default tool cache without RUNNER_TOOL_CACHE", () => {
+		const original = process.env.RUNNER_TOOL_CACHE;
+		delete process.env.RUNNER_TOOL_CACHE;
+		try {
+			expect(sdkCachePath("3.29.0", "stable", "x64")).toContain(
+				"/opt/hostedtoolcache",
+			);
+		} finally {
+			if (original !== undefined) {
+				process.env.RUNNER_TOOL_CACHE = original;
+			}
+		}
+	});
 });
 
 describe("isValidLocalSdk", () => {
diff --git a/__tests__/version.test.ts b/__tests__/version.test.ts
index be75cae..0d48e0a 100644
--- a/__tests__/version.test.ts
+++ b/__tests__/version.test.ts
@@ -667,6 +667,18 @@ describe("fetchManifest", () => {
 		expect(getJson).toHaveBeenCalledTimes(3);
 	});
 
+	it("wraps a non-Error rejection", async () => {
+		const getJson = vi.fn().mockRejectedValue("socket hang up");
+		HttpClient.mockImplementation(
+			class {
+				getJson = getJson;
+			},
+		);
+
+		await expect(fetchManifest("linux")).rejects.toThrow("socket hang up");
+		expect(getJson).toHaveBeenCalledTimes(3);
+	});
+
 	it("does not retry on HTTP 403", async () => {
 		const getJson = vi
 			.fn()