Adding unit tests for File.isAbsolute() method.

test/Files.java

@@ -0,0 +1,29 @@
+import java.io.File;
+
+public class Files {
+  private static void expect(boolean v) {
+    if (! v) throw new RuntimeException();
+  }
+  
+  private static void isAbsoluteTest(boolean absolutePath) {
+    File file = new File("test.txt");
+    if (absolutePath) {
+      file = file.getAbsoluteFile();
+    }
+    
+    boolean isAbsolute = file.isAbsolute();
+    
+    if (absolutePath) {
+      expect(isAbsolute);
+    } else {
+      expect(!isAbsolute);
+    }
+    
+  }
+  
+  public static void main(String[] args) {
+    isAbsoluteTest(true);
+    isAbsoluteTest(false);
+  }
+
+}