Capturing and simulating with two Hoverfly instances misbehaves

[larsthorup]

Description of the bug

As described elsewhere (SpectoLabs/hoverfly#864 (comment)) we are using Hoverfly to auto-mock requests in service tests. We want to CAPTURE requests to the service-under-test while SIMULATING requests to external-services. It appears that Hoverfly does not (yet) support capturing and simulating through the same instance, so we are trying to orchestrate 2 Hoverfly instances. Starting them in either order gives different issues.

When starting Hoverfly first in Capture mode, then another instance in Simulate mode, the capture file ends up only including request/response-pairs from the interaction with the Hoverfly Admin end points. See https://github.com/larsthorup/hoverfly-capture-simulate/blob/master/src/test/java/com/example/hoverfly/HoverflyDemoApplicationIntegrationTests.java#L92

When starting Hoverfly first in Simulate mode, then another instance in Capture mode, the simulation is not taking effect, meaning that calls go through to the external service instead of being replayed. See https://github.com/larsthorup/hoverfly-capture-simulate/blob/master/src/test/java/com/example/hoverfly/HoverflyDemoApplicationIntegrationTests.java#L128

Steps to reproduce the issue

Please checkout this repo with code to reproduce this issue:

• https://github.com/larsthorup/hoverfly-capture-simulate

The repo contains a small Spring Boot service (service-under-test) that invokes time.jsontest.com (external-service). The relevant part of the tests are linked above. Note, that the tests will pass to show that the issues described above have been reproduced.

Observed result

Either simulate doesn't happen, or the relevant request isn't captured, as explained above.

Expected result

Being able to simulate the external request to time.jsontest.com while simultaneously capturing the request to our own end-point /service/time.

Additional relevant information

If not indicated above:

1. Hoverfly Java version: 0.12.2

[larsthorup]

I have extended the reproduction code with a new file https://github.com/larsthorup/hoverfly-capture-simulate/blob/master/src/test/java/com/example/hoverfly/HoverflyDemoApplicationExtensionIntegrationTests.java containing a test that uses Hoverfly.extensions instead of nested Hoverfly instances.

Again, this test passes as is, because Capture is not enabled. If you enable Capture by uncommenting the @BeforeAll and @AfterAll the Capture will work but the Simulate will no longer work and the tests will fail.

Is it possible to run Capture and Simulate via two Hoverfly instances at all? Should these examples work? Are there any work-arounds to make this work?

[larsthorup]

I think I found a work-around to make this work. I have pushed an update to the repo with the reproduction code:

• https://github.com/larsthorup/hoverfly-capture-simulate/blob/master/src/test/java/com/example/hoverfly/HoverflyDemoApplicationIntegrationTests.java#L164

This is what I believe makes it work:

1. Starting the hoverflySimulate instance last means that this proxy is what will be used by the service-under-test when it makes requests to external-service, meaning that these requests will be simulated as expected.
2. Explicitly setting proxy settings for the request from the test to the service-under-test to make it use the hoverflyCapture instance, meaning that this request will be captured as expected.

Is this a good approach? Can we expect this to continue to work with future versions of Hoverfly and Hoverfly Java? Are there any drawbacks or caveats that we should be aware of?

[tommysitu]

@larsthorup I'll def check it out this weekend.

[tommysitu]

I've added a PR for your repo which should explain it: larsthorup/hoverfly-capture-simulate#1

What you're doing is fine. You just need to make sure HoverflySimulate always starts after HoverflyCapture as the start method set the JVM proxy.

A long term solution would be introducing a method to start Hoverfly without setting the proxy, such as startWithoutSettingProxy, but the use case for that is so rare.

[tommysitu]

Please close this issue if you're happy :)

[larsthorup]

Thank you for the comments! I have merged the PR and cleaned up the code a bit. We will follow this approach.