(#109) Restructured sleep tests to use deltas

Author: s1hofmann

lib/sleep.function.spec.ts

@@ -1,5 +1,7 @@
 import {busyWaitForNanoSeconds, sleep} from "./sleep.function";
 
+const maxTimeDeltaInMs = 3;
+
 describe("sleep", () => {
     it("should resolve after x ms", async () => {
         // GIVEN
@@ -9,24 +11,25 @@ describe("sleep", () => {
         const before = Date.now();
         await sleep(timeout);
         const after = Date.now();
+        const delta = Math.abs(after - before);
 
         // THEN
-        expect(after - before).toBeGreaterThanOrEqual(timeout);
+        expect(delta).toBeLessThanOrEqual(maxTimeDeltaInMs);
     });
 });
 
 describe("busyWaitForNanoSeconds", () => {
     it("should resolve after x ns", async () => {
         // GIVEN
         const timeoutNs = 5_000_000;
-        const timeoutMs = 5;
 
         // WHEN
         const before = Date.now();
         await busyWaitForNanoSeconds(timeoutNs);
         const after = Date.now();
+        const delta = Math.abs(after - before);
 
         // THEN
-        expect(after - before).toBeGreaterThanOrEqual(timeoutMs);
+        expect(delta).toBeLessThanOrEqual(maxTimeDeltaInMs);
     });
 });