diff --git a/.github/workflows/test.yml b/.github/workflows/test.yml
new file mode 100644
index 0000000..588cafe
--- /dev/null
+++ b/.github/workflows/test.yml
@@ -0,0 +1,137 @@
+name: Run Tests
+on: [push, pull_request]
+
+jobs:
+  build:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v1
+      - uses: actions/setup-java@v3
+        with:
+          distribution: temurin
+          java-version: |
+            8
+            16
+            17
+
+      # Can't use setup-java for this because https://github.com/actions/setup-java/issues/366
+      - uses: actions/cache@v3
+        with:
+          path: ~/.gradle/wrapper
+          key: gradle-wrapper-${{ hashFiles('**/gradle-wrapper.properties') }}
+      - uses: actions/cache@v3
+        with:
+          path: ~/.gradle/caches
+          key: gradle-caches-${{ hashFiles('**/*.gradle*') }}-${{ hashFiles('**/gradle.properties', 'gradle/*.versions.toml') }}
+          restore-keys: |
+            gradle-caches-${{ hashFiles('**/*.gradle*') }}
+            gradle-caches-
+
+      - run: ./gradlew build -x integrationTest setupDownloadsApi --stacktrace
+
+      - uses: actions/upload-artifact@v3
+        if: ${{ failure() || success() }}
+        with:
+          name: Raw Test Results
+          path: "**/build/test-results/**/*.xml"
+          retention-days: 1 # only for the report at the end
+
+      - uses: actions/upload-artifact@v3
+        if: ${{ failure() }}
+        with:
+          name: Unit Test Results
+          path: "**/build/reports/"
+
+      - uses: actions/cache/save@v3
+        with:
+          path: |
+            **/.gradle
+            **/build
+          key: test-build-${{ github.run_id }}-${{ github.run_attempt }}
+
+  prepare_integration_test_matrix:
+    needs: build # don't even bother with tests if it doesn't even build
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v3
+      - uses: actions/github-script@v6
+        id: create-matrix
+        with:
+          script: |
+            const tests = []
+            for (platform of ["launchwrapper", "fabric"]) {
+              const prefix = `integrationTest/${platform}/src/main/java/`
+              for await (const file of (await glob.create(`${prefix}/**/*Tests.java`)).globGenerator()) {
+                const cls = file.slice(file.indexOf(prefix) + prefix.length, file.length - 5).replaceAll("/", ".")
+                tests.push({ platform, "class": cls })
+              }
+            }
+            return tests
+          github-token: dummy # we don't need one but it'll complain without one (when running locally via act)
+    outputs:
+      matrix: ${{ steps.create-matrix.outputs.result }}
+
+  integration_tests:
+    needs:
+      - prepare_integration_test_matrix
+      - build # we'll want to re-use the caches it produces
+    strategy:
+      fail-fast: false
+      max-parallel: 1
+      matrix:
+        test: ${{ fromJson(needs.prepare_integration_test_matrix.outputs.matrix) }}
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v3
+      - uses: actions/cache/restore@v3
+        with:
+          path: |
+            **/.gradle
+            **/build
+          key: test-build-${{ github.run_id }}-${{ github.run_attempt }}
+          fail-on-cache-miss: true
+
+      - uses: actions/setup-java@v3
+        with:
+          distribution: temurin
+          java-version: |
+            8
+            16
+            17
+      - uses: actions/cache/restore@v3
+        with:
+          path: ~/.gradle/wrapper
+          key: gradle-wrapper-${{ hashFiles('**/gradle-wrapper.properties') }}
+      - uses: actions/cache/restore@v3
+        with:
+          path: ~/.gradle/caches
+          key: gradle-caches-${{ hashFiles('**/*.gradle*') }}-${{ hashFiles('**/gradle.properties', 'gradle/*.versions.toml') }}
+
+      - run: ./gradlew :integrationTest:${{ matrix.test.platform }}:integrationTest --tests ${{ matrix.test.class }} --stacktrace --info
+
+      - uses: actions/upload-artifact@v3
+        if: ${{ failure() || success() }}
+        with:
+          name: Raw Test Results
+          path: integrationTest/${{ matrix.test.platform }}/build/test-results/**/*.xml
+          retention-days: 1 # only for the report at the end
+
+      - uses: actions/upload-artifact@v3
+        if: ${{ failure() }}
+        with:
+          name: ${{ matrix.test.platform }}:${{ matrix.test.class }} Results
+          path: integrationTest/${{ matrix.test.platform }}/build/reports/
+
+  test_report:
+    runs-on: ubuntu-latest
+    needs: [build, integration_tests]
+    if: ${{ !cancelled() }}
+    steps:
+      - name: Download artifacts
+        uses: actions/download-artifact@v3
+        with:
+          path: artifacts
+      - name: Publish test report
+        uses: EnricoMi/publish-unit-test-result-action@d93dbc08d265e4653da0c0af544bee2a851d3e38 # v2.10.0
+        with:
+          junit_files: "artifacts/**/*.xml"
diff --git a/stage0/build.gradle b/stage0/build.gradle
index 5d443a6..3364493 100644
--- a/stage0/build.gradle
+++ b/stage0/build.gradle
@@ -40,13 +40,15 @@ configure(subprojects.findAll { it.name != "common" && it.name != "modlauncher"
         }
 
         repositories {
-            maven {
-                name 'nexus'
-                url "https://repo.sk1er.club/repository/maven-${this.properties.getOrDefault("IS_CI", false) ? "snapshots" : "releases"}/"
-
-                credentials {
-                    username project.nexus_user
-                    password project.nexus_password
+            if (project.hasProperty("nexus_user")) {
+                maven {
+                    name 'nexus'
+                    url "https://repo.sk1er.club/repository/maven-${this.properties.getOrDefault("IS_CI", false) ? "snapshots" : "releases"}/"
+
+                    credentials {
+                        username project.nexus_user
+                        password project.nexus_password
+                    }
                 }
             }
         }
diff --git a/stage2/common/src/main/java/gg/essential/loader/stage2/jvm/ForkedJvmLoaderSwingUI.java b/stage2/common/src/main/java/gg/essential/loader/stage2/jvm/ForkedJvmLoaderSwingUI.java
index 8382cf0..45cd881 100644
--- a/stage2/common/src/main/java/gg/essential/loader/stage2/jvm/ForkedJvmLoaderSwingUI.java
+++ b/stage2/common/src/main/java/gg/essential/loader/stage2/jvm/ForkedJvmLoaderSwingUI.java
@@ -2,9 +2,19 @@
 
 import gg.essential.loader.stage2.LoaderSwingUI;
 
+import java.awt.*;
 import java.io.IOException;
 
 public class ForkedJvmLoaderSwingUI extends ForkedJvmLoaderUI {
+    @Override
+    public void start() {
+        // Skip actual GUI for integration tests if we're in a headless environment
+        if (System.getProperty("essential.integration_testing") != null && GraphicsEnvironment.isHeadless()) {
+            return;
+        }
+        super.start();
+    }
+
     public static void main(String[] args) throws IOException {
         forked(new LoaderSwingUI());
     }