Add basic CI setup

Combines both test workspaces into a single one to reduce the number of
jobs.

.github/workflows/test.yml

@@ -0,0 +1,41 @@
+name: Test
+
+on:
+  push:
+    branches: [ main ]
+  pull_request:
+    branches: [ main ]
+
+jobs:
+
+  build_test_main:
+    name: Build and test (main repository)
+    runs_on: ${{ matrix.os }}
+    matrix:
+      os: [ubuntu-latest, macos-latest, windows-latest]
+
+  steps:
+    - uses: actions/checkout@v2
+
+    - name: Build
+      run: bazelisk build //...
+
+    - name: Test
+      run: bazelisk test //...
+
+  build_test_test:
+    name: Build and test (test repository)
+    runs_on: ${{ matrix.os }}
+    matrix:
+      os: [ubuntu-latest, macos-latest, windows-latest]
+
+  steps:
+    - uses: actions/checkout@v2
+
+    - name: Build
+      working-directory: test
+      run: bazelisk build //...
+
+    - name: Test
+      working-directory: test
+      run: bazelisk test //...

test/WORKSPACE

@@ -19,4 +19,13 @@ jvm_maven_import_external(
     server_urls = ["https://repo.maven.apache.org/maven2"],
 )
 
+jvm_maven_import_external(
+    name = "org_twitter4j_twitter4j_core",
+    artifact = "org.twitter4j:twitter4j-core:4.0.7",
+    artifact_sha256 = "f3d28049f1c13752c2ea71397fdcda8d9723cf315e7101502997fddfe9aad66d",
+    server_urls = ["https://repo.maven.apache.org/maven2"],
+)
+
 jar_jar_repositories()
+
+register_toolchains("//jar_jar_aspect:jar_jar_toolchain")