Adding ES6 module checks for each warning type in CheckInterfacesTest…

… of the LINTCHECKS pass. Part of verification/adding of ES6 module compatibility to compiler.

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Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=159856269

test/com/google/javascript/jscomp/lint/CheckInterfacesTest.java

@@ -48,19 +48,21 @@ public void testInterfaceArgs() throws Exception {
     testSame("/** @interface */ function A(x) {}",
         CheckInterfaces.INTERFACE_SHOULD_NOT_TAKE_ARGS);
 
-    testSame("var ns = {};\n"
-        + "/** @interface */\n"
-        + "ns.SomeInterface = function(x) {};",
+    testSame(
+        LINE_JOINER.join(
+            "var ns = {};\n", "/** @interface */\n", "ns.SomeInterface = function(x) {};"),
         CheckInterfaces.INTERFACE_SHOULD_NOT_TAKE_ARGS);
   }
 
   public void testInterfaceNotEmpty() {
     testSame("/** @interface */ function A() { this.foo; }",
         CheckInterfaces.INTERFACE_FUNCTION_NOT_EMPTY);
 
-    testSame("var ns = {};\n"
-        + "/** @interface */\n"
-        + "ns.SomeInterface = function() { this.foo; };",
+    testSame(
+        LINE_JOINER.join(
+            "var ns = {};\n",
+            "/** @interface */\n",
+            "ns.SomeInterface = function() { this.foo; };"),
         CheckInterfaces.INTERFACE_FUNCTION_NOT_EMPTY);
   }
 }