Try to test it

jest.setup.ts

@@ -1,3 +1,5 @@
+import { MatcherFunction } from 'expect'
+
 declare global {
   namespace jest {
     interface Matchers<R> {
@@ -6,6 +8,12 @@ declare global {
         message: string
       ): R;
     }
+    interface Expect {
+      matchesPredicate(predicate: (actual: any) => boolean): any
+    }
+    interface ExpectExtendMap {
+      matchesPredicate: MatcherFunction<[predicate: (actual: any) => boolean]>
+    }
   }
 }
 
@@ -59,6 +67,12 @@ But instead it was:
       message: () => "Expected function to throw but it did not",
     };
   },
+  matchesPredicate(actual: any, predicate: (actual: any) => boolean) {
+    return {
+      pass: predicate(actual),
+      message: () => "Expected object that passes predicate",
+    };
+  },
 });
 
 export default undefined;

src/domain/release-archive.spec.ts

@@ -70,7 +70,17 @@ describe("fetch", () => {
 
     expect(axiosRetry).toHaveBeenCalledWith(axios, {
       retries: 3,
-      retryDelay: axiosRetry.exponentialDelay,
+      retryDelay: expect.matchesPredicate((retryDelayFn: Function) => {
+        // Make sure the retry delays follow exponential backoff
+        // and the final retry happens after at least 1 minute total.
+        let firstRetryDelay = retryDelayFn(0);
+        let secondRetryDelay = retryDelayFn(1);
+        let thirdRetryDelay = retryDelayFn(2);
+        return 10000 <= firstRetryDelay && firstRetryDelay <= 12000
+          && 20000 <= secondRetryDelay && secondRetryDelay <= 24000
+          && 40000 <= thirdRetryDelay && thirdRetryDelay <= 48000;
+      }),
+      shouldResetTimeout: true,
     });
   });
 

src/domain/release-archive.ts

@@ -108,7 +108,7 @@ export class ReleaseArchive {
   }
 }
 
-function exponentialDelay(retryCount: number, error: AxiosError): number {
+function exponentialDelay(retryCount: number, error: AxiosError = undefined): number {
     // Using exponential backoff with 3 retries and a delay factor of 10 seconds
     // gives you at least 70 seconds to publish a release archive.
     const tenSeconds = 10000;