Add testcases

Author: StevenWong12

Tests/SwiftSyntaxBuilderTest/CollectionNodeFlatteningTests.swift

@@ -46,4 +46,19 @@ final class CollectionNodeFlatteningTests: XCTestCase {
       """
     )
   }
+
+  func test_FlattenCodeBlockItemListWithCodeBlockStrings() {
+    let buildable = CodeBlockItemListSyntax {
+      "let one = object.methodOne()"
+      "let two = object.methodTwo()"
+    }
+
+    AssertBuildResult(
+      buildable,
+      """
+      let one = object.methodOne()
+      let two = object.methodTwo()
+      """
+    )
+  }
 }

Tests/SwiftSyntaxBuilderTest/StringInterpolationTests.swift

@@ -460,4 +460,23 @@ final class StringInterpolationTests: XCTestCase {
       )
     }
   }
+
+  func testCodeBlockItemInterpolation() {
+    let codeBlock = CodeBlockItemSyntax(
+      """
+      func foo() {
+        return bar
+      }
+      """
+    )
+
+    AssertStringsEqualWithDiff(
+      codeBlock.description,
+      """
+      func foo() {
+        return bar
+      }
+      """
+    )
+  }
 }