diff --git a/.github/workflows/main.yml b/.github/workflows/main.yml
new file mode 100644
index 0000000000..419e6f27a3
--- /dev/null
+++ b/.github/workflows/main.yml
@@ -0,0 +1,32 @@
+name: Main
+on:
+  - pull_request # without merge conflicts
+  - push # branch or tag
+
+concurrency:
+  group: ${{ github.workflow }}-${{ github.ref }}
+  cancel-in-progress: true
+
+jobs:
+  main:
+    strategy:
+      fail-fast: false
+      matrix:
+        os: [ macos-latest, ubuntu-latest, windows-latest ]
+        dc: [ dmd-latest, ldc-latest ]
+    name: ${{ matrix.os }}, ${{ matrix.dc }}
+    runs-on: ${{ matrix.os }}
+    timeout-minutes: 10
+    steps:
+      - uses: actions/checkout@v4
+      - name: Install D compiler
+        uses: dlang-community/setup-dlang@v1.3.0
+        with:
+          compiler: ${{ matrix.dc }}
+      - name: Build
+        shell: bash
+        run: make -j3 DMD=${{ startsWith(matrix.dc, 'ldc') && 'ldmd2' || 'dmd' }}
+      - name: Test
+        shell: bash
+        # /tmp is a symlink on Mac, and rdmd_test.d doesn't like it
+        run: ${{ startsWith(matrix.os, 'macos') && 'TMPDIR=$(cd /tmp && pwd -P)' || '' }} make -j3 DMD=${{ startsWith(matrix.dc, 'ldc') && 'ldmd2' || 'dmd' }} test
diff --git a/Makefile b/Makefile
index e13efd2654..31b42df143 100644
--- a/Makefile
+++ b/Makefile
@@ -97,12 +97,19 @@ $(ROOT)/tests_extractor$(DOTEXE): tests_extractor.d
 # Build & run tests
 ################################################################################
 
+ifeq (windows,$(OS))
+    # for some reason, --strip-trailing-cr isn't enough - need to dos2unix stdin
+    DIFF := dos2unix | diff --strip-trailing-cr
+else
+    DIFF := diff
+endif
+
 test_tests_extractor: $(ROOT)/tests_extractor$(DOTEXE)
 	for file in ascii iteration ; do \
-		$< -i "./test/tests_extractor/$${file}.d" | diff --strip-trailing-cr -p - "./test/tests_extractor/$${file}.d.ext"; \
+		$< -i "./test/tests_extractor/$${file}.d" | $(DIFF) -u -p - "./test/tests_extractor/$${file}.d.ext"; \
 	done
-	$< -a betterc -i "./test/tests_extractor/attributes.d" | diff --strip-trailing-cr -p - "./test/tests_extractor/attributes.d.ext";
-	$< --betterC -i "./test/tests_extractor/betterc.d" | diff --strip-trailing-cr -p - "./test/tests_extractor/betterc.d.ext";
+	$< -a betterc -i "./test/tests_extractor/attributes.d" | $(DIFF) -u -p - "./test/tests_extractor/attributes.d.ext";
+	$< --betterC -i "./test/tests_extractor/betterc.d" | $(DIFF) -u -p - "./test/tests_extractor/betterc.d.ext";
 
 RDMD_TEST_COMPILERS = $(DMD)
 RDMD_TEST_EXECUTABLE = $(ROOT)/rdmd$(DOTEXE)
diff --git a/rdmd_test.d b/rdmd_test.d
index 706538bb3a..881569887f 100755
--- a/rdmd_test.d
+++ b/rdmd_test.d
@@ -431,7 +431,7 @@ void runTests(string rdmdApp, string compiler, string model)
 
         res = execute(rdmdArgs ~ [forceSrc.baseName()]);
         enforce(res.status == 0, res.output);
-        enforce(!res.output.canFind("compile_force_src"));
+        enforce(!res.output.canFind("compile_force_src"), res.output);
     }
 
     auto conflictDir = forceSrc.setExtension(".dir");
@@ -684,11 +684,11 @@ void runFallbackTest(string rdmdApp, string buildCompiler, string model)
        if an explicit --compiler flag is not provided, rdmd should
        search its own binary path first when looking for the default
        compiler (determined by the compiler used to build it) */
-    string localDMD = buildPath(tempDir(), baseName(buildCompiler).setExtension(binExt));
+    string localDMD = buildPath(dirName(rdmdApp), baseName(buildCompiler).setExtension(binExt));
     std.file.write(localDMD, ""); // An empty file avoids the "Not a valid 16-bit application" pop-up on Windows
     scope(exit) std.file.remove(localDMD);
 
     auto res = execute(rdmdApp ~ [modelSwitch(model), "--force", "--chatty", "--eval=writeln(`Compiler found.`);"]);
     enforce(res.status == 1, res.output);
-    enforce(res.output.canFind(format(`spawn [%(%s%),`, localDMD.only)), localDMD ~ " would not have been executed");
+    enforce(res.output.canFind(format(`spawn [%(%s%),`, localDMD.only)), localDMD ~ " would not have been executed. Output:\n" ~ res.output);
 }