ci: build and run a test Docker image

.dockerignore

@@ -0,0 +1,3 @@
+.git
+.gitea
+codex-ssh-test.md

.gitea/workflows/test.yaml

@@ -8,6 +8,9 @@ jobs:
       image: ubuntu:latest
 
     steps:
+      - name: Checkout Repository
+        uses: actions/checkout@v4
+
       - name: Say Hello
         run: echo "Testing connection..."
 
@@ -31,4 +34,14 @@ jobs:
           echo "正在嘗試連線 Docker API..."
           echo "DOCKER_HOST = $DOCKER_HOST"
           docker ps
-          echo "成功！可以看到上面的容器列表了！"
+          echo "成功！可以看到上面的容器列表了！"
+
+      - name: Build Test Image
+        run: |
+          docker build --progress=plain -t test-runner:ci .
+
+      - name: Run Test Image
+        run: |
+          output="$(docker run --rm test-runner:ci)"
+          echo "$output"
+          test "$output" = "Gitea Runner Docker build succeeded."

Dockerfile

@@ -0,0 +1,15 @@
+FROM alpine:3.22.5 AS builder
+
+RUN apk add --no-cache build-base
+
+WORKDIR /src
+COPY hello.c .
+
+RUN mkdir -p /out \
+    && cc -O2 -Wall -Wextra -Werror -static hello.c -o /out/hello
+
+FROM scratch
+
+COPY --from=builder /out/hello /hello
+
+ENTRYPOINT ["/hello"]

hello.c

@@ -0,0 +1,7 @@
+#include <stdio.h>
+
+int main(void)
+{
+    puts("Gitea Runner Docker build succeeded.");
+    return 0;
+}