Admin - Parallelize TF test runs in CI (#4177)

.github/workflows/build.yml

@@ -203,8 +203,10 @@ jobs:
     runs-on: ubuntu-latest
     needs: terraformcache
     strategy:
+      fail-fast: false
       matrix:
         python-version: [ 3.8 ]
+        part: ["aa", "ab", "ac"]
 
     steps:
     - uses: actions/checkout@v2
@@ -231,10 +233,17 @@ jobs:
         python setup.py sdist
         docker run --rm -t --name motoserver -e TEST_SERVER_MODE=true -e MOTO_PORT=4566 -e AWS_SECRET_ACCESS_KEY=server_secret -e AWS_ACCESS_KEY_ID=server_key -v `pwd`:/moto -p 4566:4566 -v /var/run/docker.sock:/var/run/docker.sock python:3.7-buster /moto/travis_moto_server.sh &
         MOTO_PORT=4566 python wait_for.py
+    # Poor man's parallelization
+    # Running them sequentially takes to much time
+    # And using the build in parallel-argument does not help with reducing runtime
+    # So we simply split the list of tests, and ask our CI for separate VM's to run them in parallel
+    - name: Get list of tests
+      run: |
+        split -n l/3 tests/terraform-tests.success.txt tf-split-
     - name: Run Terraform Tests
       run: |
         cd moto-terraform-tests
-        AWS_DEFAULT_REGION=us-east-1 AWS_ALTERNATE_REGION=eu-west-1 bin/run-tests -t -i ../tests/terraform-tests.success.txt -e ../tests/terraform-tests.failures.txt
+        AWS_DEFAULT_REGION=us-east-1 AWS_ALTERNATE_REGION=eu-west-1 bin/run-tests -t -i ../tf-split-${{ matrix.part }} -e ../tests/terraform-tests.failures.txt
         cd ..
     - name: "Create report"
       run: |