add a gradle demo

.gitignore

@@ -3,6 +3,7 @@ target/
 
 # gradle ignore
 build/
+out/
 .gradle/
 
 # eclipse ignore

demo/java-demo/build.gradle

@@ -0,0 +1,23 @@
+plugins {
+    id 'java'
+}
+
+group = 'com.alibaba.testable'
+version = '1.0.0-SNAPSHOT'
+sourceCompatibility = '8'
+
+repositories {
+    mavenCentral()
+}
+
+dependencies {
+    testImplementation('org.junit.jupiter:junit-jupiter:5.6.2')
+    testImplementation('com.alibaba.testable:testable-processor:0.3.2-SNAPSHOT')
+    testAnnotationProcessor('com.alibaba.testable:testable-processor:0.3.2-SNAPSHOT')
+    testRuntimeOnly('com.alibaba.testable:testable-agent:0.3.2-SNAPSHOT')
+}
+
+test {
+    jvmArgs "-javaagent:${classpath.find { it.name.contains("testable-agent") }.absolutePath}"
+    useJUnitPlatform()
+}

docs/zh-cn/doc/setup.md

@@ -80,4 +80,4 @@ test {
 }
 ```
 
-> 该配置尚未在Gradle项目上经过实际验证，可行性待确认。
+> 注意：由于Gradle的构建与测试运行机制与Maven稍有差异，当前在Gradle项目里，`@PrivateAccessor`注解和`TestableTool.TEST_CASE`功能存在已知BUG，其余功能均可正常使用