Retry E2E tests on failure if running in CI. (#995)

* Retry E2E tests in CI

* newsfile

Author: Half-Shot

changelog.d/995.misc

@@ -0,0 +1 @@
+Retry e2e tests in CI due to container creation flakiness.

jest.config.ts

@@ -9,6 +9,7 @@ const config: Config = {
   // The root directory that Jest should scan for tests and modules within
   rootDir: "spec-lib",
   testTimeout: 60000,
+  setupFiles: ["<rootDir>/spec/setup-jest.js"],
 };
 
 export default config;

spec/setup-jest.ts

@@ -0,0 +1,2 @@
+// In CI, the network creation for the homerunner containers can race (https://github.com/matrix-org/complement/issues/720).
+jest.retryTimes(process.env.CI ? 3 : 1);