Added JUnit Test Cases for Replacement

core/src/test/java/com/google/googlejavaformat/java/ReplacementTest.java

@@ -0,0 +1,61 @@
+/*
+ * Copyright 2025 Google Inc.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except
+ * in compliance with the License. You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software distributed under the License
+ * is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express
+ * or implied. See the License for the specific language governing permissions and limitations under
+ * the License.
+ */
+
+package com.google.googlejavaformat.java;
+
+import static com.google.common.truth.Truth.assertThat;
+import static org.junit.Assert.*;
+
+import com.google.common.collect.Range;
+import com.google.common.testing.EqualsTester;
+import org.junit.Test;
+import org.junit.runner.RunWith;
+import org.junit.runners.JUnit4;
+
+/** {@link Replacement}Test */
+@RunWith(JUnit4.class)
+public class ReplacementTest {
+
+    @Test
+    public void testCreateWithValidInput() {
+        Replacement replacement = Replacement.create(3, 7, "replacementText");
+        assertThat(replacement.getReplaceRange()).isEqualTo(Range.closedOpen(3, 7));
+        assertThat(replacement.getReplacementString()).isEqualTo("replacementText");
+    }
+
+    @Test
+    public void testCreateWithNegativeStartPositionThrows() {
+        assertThrows(IllegalArgumentException.class, () -> Replacement.create(-1, 5, "text"));
+    }
+
+    @Test
+    public void testCreateWithStartPositionAfterEndPositionThrows() {
+        assertThrows(IllegalArgumentException.class, () -> Replacement.create(10, 5, "text"));
+    }
+
+    @Test
+    public void testEqualsAndHashCode() {
+        Replacement replacement = Replacement.create(0, 4, "abc");
+        Replacement replacementCopy = Replacement.create(0, 4, "abc");
+        Replacement differentStart = Replacement.create(1, 4, "abc");
+        Replacement differentText = Replacement.create(0, 4, "def");
+
+        new EqualsTester()
+                .addEqualityGroup(replacement, replacementCopy)
+                .addEqualityGroup(differentStart)
+                .addEqualityGroup(differentText)
+                .testEquals();
+    }
+
+}