feat(diff): add test case for DiffSimplifier

Add a new test case to verify the functionality of the DiffSimplifier class. The test case includes setting up the necessary dependencies and calling the simplify method with a list of changes and ignore file patterns. Assertions can be added to verify the simplified diff.

src/test/kotlin/cc/unitmesh/devti/prompting/diff/DiffSimplifierTest.kt

@@ -0,0 +1,23 @@
+package cc.unitmesh.devti.prompting.diff;
+
+import com.intellij.openapi.vcs.changes.Change
+import com.intellij.testFramework.fixtures.LightPlatformCodeInsightFixture4TestCase
+import java.nio.file.PathMatcher
+
+class DiffSimplifierTest : LightPlatformCodeInsightFixture4TestCase() {
+    private lateinit var diffSimplifier: DiffSimplifier
+
+    override fun setUp() {
+        super.setUp()
+        diffSimplifier = DiffSimplifier(project)
+    }
+
+    fun testSimplify() {
+        val changes = listOf<Change>() // Add test changes here
+        val ignoreFilePatterns = listOf<PathMatcher>() // Add test ignore file patterns here
+
+        val simplifiedDiff = diffSimplifier.simplify(changes, ignoreFilePatterns)
+
+        // Add assertions here to verify the simplified diff
+    }
+}