开始编写例子

app/src/test/java/com/example/arial/downloaddemo/ExampleUnitTest.java

@@ -2,14 +2,13 @@ package com.example.arial.downloaddemo;
 
 import org.junit.Test;
 
-import static org.junit.Assert.*;
+import static org.junit.Assert.assertEquals;
 
 /**
  * To work on unit tests, switch the Test Artifact in the Build Variants view.
  */
 public class ExampleUnitTest {
-    @Test
-    public void addition_isCorrect() throws Exception {
-        assertEquals(4, 2 + 2);
-    }
+  @Test public void addition_isCorrect() throws Exception {
+    assertEquals(4, 2 + 2);
+  }
 }