add github CI test workflow

.github/workflows/ci.yml

@@ -77,6 +77,25 @@ jobs:
           command: build
           args: --release --features semihosting
 
+  test:
+    runs-on: ubuntu-latest
+    strategy:
+      matrix:
+        toolchain:
+          - stable
+          - beta
+    steps:
+      - uses: actions/checkout@v2
+      - name: Install Rust ${{ matrix.toolchain }}
+        uses: actions-rs/toolchain@v1
+        with:
+          toolchain: ${{ matrix.toolchain }}
+      - name: cargo test
+        uses: actions-rs/cargo@v1
+        with:
+          command: test
+          args: --manifest-path dsp/Cargo.toml --target=x86_64-unknown-linux-gnu
+
   # Tell bors about it
   # https://github.com/rtic-rs/cortex-m-rtic/blob/8a4f9c6b8ae91bebeea0791680f89375a78bffc6/.github/workflows/build.yml#L566-L603
   ci-success: