Create separate test workflow for docker

This expands on the current testing suite a bit by introducing a new
workflow for testing functionality within the docker container. It runs
the same test suite as the regular "test" workflow, but also performs a
health check after running the app for 10 seconds to ensure
functionality.

The buildx workflow now waits for the docker test script to finish
successfully, rather than the regular test workflow. This will hopefully
avoid situations where new images are pushed with issues that aren't
detected in regular testing of the app.

.github/workflows/buildx.yml

@@ -2,7 +2,7 @@ name: buildx
 
 on:
   workflow_run:
-    workflows: ["tests"]
+    workflows: ["docker_tests"]
     branches: [main]
     types:
       - completed

.github/workflows/docker_tests.yml

@@ -0,0 +1,19 @@
+name: docker_tests
+
+on: [push, pull_request]
+
+jobs:
+  test:
+    runs-on: ubuntu-latest
+    steps:
+    - name: checkout code
+      uses: actions/checkout@v2
+    - name: build and test
+      run: |
+        docker build --tag whoogle-search:test .
+        TEST_CONTAINER=$(docker run --entrypoint=/bin/bash --detach whoogle-search:test)
+        docker cp test "$TEST_CONTAINER":/whoogle/test
+        docker exec "$TEST_CONTAINER" ./run test
+        docker exec --detach "$TEST_CONTAINER" ./run
+        sleep 10
+        docker exec "$TEST_CONTAINER" curl -f http://localhost:5000/healthz || exit 1