Simplify exponential backoff test cases

__tests__/index/retryConnectionDelay.test.ts

@@ -68,71 +68,74 @@ describe("Exponential backoff delay", () => {
   describe("with rate 2, backoffLimit 8000 ms", () => {
     // The initial delay shall be 1 s
     const initialDelay = 1000;
-    const exponentialBackoffParams: ExponentialBackoffParams = {
+    const exponentialBackoff: ExponentialBackoffParams = {
       backoffRate: 2,
       // We put the ceiling at exactly 8000 ms
       backoffLimit: 8000,
     };
+    const attempts: [number, number][] = [
+      [1000, 0],
+      [2000, 1],
+      [4000, 2],
+      [8000, 3],
+      [8000, 4],
+    ];
     it("will never be more than 8000 ms with rate set to 2", () => {
-      expect(
-        calculateRetryDelayFactor(exponentialBackoffParams, initialDelay, 0),
-      ).toBe(1000);
-      expect(
-        calculateRetryDelayFactor(exponentialBackoffParams, initialDelay, 1),
-      ).toBe(2000);
-      expect(
-        calculateRetryDelayFactor(exponentialBackoffParams, initialDelay, 2),
-      ).toBe(4000);
-      expect(
-        calculateRetryDelayFactor(exponentialBackoffParams, initialDelay, 3),
-      ).toBe(8000);
-      expect(
-        calculateRetryDelayFactor(exponentialBackoffParams, initialDelay, 4),
-      ).toBe(8000);
+      attempts.forEach(([delay, failedAttempts]) => {
+        expect(
+          calculateRetryDelayFactor(
+            exponentialBackoff,
+            initialDelay,
+            failedAttempts,
+          ),
+        ).toBe(delay);
+      });
     });
 
     it("should delay reconnection attempts exponentially", async () => {
+      // Somehow we need to convincen typescript here that "WebSocket" is
+      // totally valid. Could be because it doesn't assume WebSocket is part of
+      // global / the index key is missing
       const webSocketSpy = jest.spyOn(global, "WebSocket" as any);
       webSocketSpy.mockImplementation(() => {});
       const setTimeoutSpy = jest.spyOn(global, "setTimeout");
-      const sarus = new Sarus({
-        url,
-        exponentialBackoff: exponentialBackoffParams,
-      });
+      const sarus = new Sarus({ url, exponentialBackoff });
       expect(sarus.state).toStrictEqual({
         kind: "connecting",
         failedConnectionAttempts: 0,
       });
       let instance: WebSocket;
+      // Get the first WebSocket instance, and ...
       [instance] = webSocketSpy.mock.instances;
       if (!instance.onopen) {
         throw new Error();
       }
+      // tell the sarus instance that it is open, and ...
       instance.onopen(new Event("open"));
       if (!instance.onclose) {
         throw new Error();
       }
+      // close it immediately
       instance.onclose(new CloseEvent("close"));
+      expect(sarus.state).toStrictEqual({
+        kind: "closed",
+        failedConnectionAttempts: 0,
+      });
 
       let cb: Sarus["connect"];
       // We iteratively call sarus.connect() and let it fail, seeing
       // if it reaches 8000 as a delay and stays there
-      const attempts: [number, number][] = [
-        [1000, 1],
-        [2000, 2],
-        [4000, 3],
-        [8000, 4],
-        [8000, 5],
-      ];
-      attempts.forEach(([delay, failedAttempts]: [number, number]) => {
+      attempts.forEach(([delay, failedAttempts]) => {
         const call =
           setTimeoutSpy.mock.calls[setTimeoutSpy.mock.calls.length - 1];
         if (!call) {
           throw new Error();
         }
+        // Make sure that setTimeout was called with the correct delay
         expect(call[1]).toBe(delay);
         cb = call[0];
         cb();
+        // Get the most recent WebSocket instance
         instance =
           webSocketSpy.mock.instances[webSocketSpy.mock.instances.length - 1];
         if (!instance.onclose) {
@@ -141,7 +144,7 @@ describe("Exponential backoff delay", () => {
         instance.onclose(new CloseEvent("close"));
         expect(sarus.state).toStrictEqual({
           kind: "connecting",
-          failedConnectionAttempts: failedAttempts,
+          failedConnectionAttempts: failedAttempts + 1,
         });
       });
     });