diff --git a/.github/workflows/docker-tests.yml b/.github/workflows/docker-tests.yml
new file mode 100644
index 0000000..794ba2d
--- /dev/null
+++ b/.github/workflows/docker-tests.yml
@@ -0,0 +1,18 @@
+name: Tests within Docker
+
+on:
+  push:
+    branches: [ master ]
+  pull_request:
+    branches: [ master ]
+
+jobs:
+
+  build:
+
+    runs-on: ubuntu-latest
+
+    steps:
+    - uses: actions/checkout@v2
+    - name: Build the Docker image
+      run: docker build . --file Dockerfile.tests --tag my-image-name:$(date +%s)
diff --git a/Dockerfile.tests b/Dockerfile.tests
index 55d0d06..3382958 100644
--- a/Dockerfile.tests
+++ b/Dockerfile.tests
@@ -1,4 +1,4 @@
-FROM microsoft/dotnet
+FROM mcr.microsoft.com/dotnet/core/sdk:3.1
 
 WORKDIR /app
 COPY . .
@@ -9,4 +9,4 @@ RUN dotnet restore
 RUN dotnet test
 
 # run tests on docker run
-ENTRYPOINT ["dotnet", "test"]
\ No newline at end of file
+ENTRYPOINT ["dotnet", "test"]
diff --git a/README.MD b/README.MD
index 6c07deb..b809625 100644
--- a/README.MD
+++ b/README.MD
@@ -3,7 +3,7 @@ This compiler & runtime will be improved continuously. Please be clement, as thi
 
 **Take a look at the documentation: [Almost Binary - Wiki](https://github.com/wsdt/AlmostBinary/wiki)**
 
-## Code Once, Run Everywhere. 
+## Code Once, Run Everywhere. ![Tests within Docker](https://github.com/wsdt/AlmostBinary/workflows/Tests%20within%20Docker/badge.svg)
 Code in platform-independent Binary. It was never so easy to proof that you are a real geek. 
 
 This programming language is made for people, who..