Implemented AssertThatStringIsEmpty.

src/test/resources/inspections/StringIsEmpty/StringIsEmptyBefore.java

@@ -0,0 +1,11 @@
+import static org.assertj.core.api.Assertions.assertThat;
+
+public class StringIsEmpty {
+
+    private void stringIsEmpty() {
+        String string = "string";
+
+        assertThat(string).isEqualTo("foo");
+        assertThat(string).isEqualTo("");
+    }
+}