diff --git a/crates/oxc_transformer/src/lib.rs b/crates/oxc_transformer/src/lib.rs
index a2fc951d4..7d8617e45 100644
--- a/crates/oxc_transformer/src/lib.rs
+++ b/crates/oxc_transformer/src/lib.rs
@@ -32,8 +32,12 @@ use oxc_span::SourceType;
 use oxc_traverse::{traverse_mut, Traverse, TraverseCtx};
 
 pub use crate::{
-    compiler_assumptions::CompilerAssumptions, env::EnvOptions, es2015::ES2015Options,
-    options::BabelOptions, options::TransformOptions, react::ReactOptions,
+    compiler_assumptions::CompilerAssumptions,
+    env::EnvOptions,
+    es2015::{ArrowFunctionsOptions, ES2015Options},
+    options::BabelOptions,
+    options::TransformOptions,
+    react::ReactOptions,
     typescript::TypeScriptOptions,
 };
 
diff --git a/tasks/coverage/src/suite.rs b/tasks/coverage/src/suite.rs
index fd3824a8d..0acd209bb 100644
--- a/tasks/coverage/src/suite.rs
+++ b/tasks/coverage/src/suite.rs
@@ -371,6 +371,9 @@ pub trait Case: Sized + Sync + Send + UnwindSafe {
                 writer.write_all(error.as_bytes())?;
             }
             TestResult::Mismatch(ast_string, expected_ast_string) => {
+                writer.write_all(
+                    format!("Mismatch: {:?}\n", normalize_path(self.path())).as_bytes(),
+                )?;
                 if args.diff {
                     self.print_diff(writer, ast_string.as_str(), expected_ast_string.as_str())?;
                     println!("Mismatch: {:?}", normalize_path(self.path()));
diff --git a/tasks/coverage/src/transformer.rs b/tasks/coverage/src/transformer.rs
index 029983e57..b9fb4c19d 100644
--- a/tasks/coverage/src/transformer.rs
+++ b/tasks/coverage/src/transformer.rs
@@ -1,9 +1,13 @@
 use std::path::{Path, PathBuf};
 
 use oxc_allocator::Allocator;
+use oxc_codegen::{Codegen, CodegenOptions};
 use oxc_parser::Parser;
 use oxc_span::SourceType;
-use oxc_transformer::{TransformOptions, Transformer};
+use oxc_transformer::{
+    ArrowFunctionsOptions, ES2015Options, ReactOptions, TransformOptions, Transformer,
+    TypeScriptOptions,
+};
 
 use crate::{
     babel::BabelCase,
@@ -14,16 +18,62 @@ use crate::{
 };
 
 /// Runs the transformer and make sure it doesn't crash.
-/// TODO: add codegen to turn on idempotency test.
 fn get_result(source_text: &str, source_type: SourceType, source_path: &Path) -> TestResult {
     let allocator = Allocator::default();
-    let ret = Parser::new(&allocator, source_text, source_type).parse();
-    let mut program = ret.program;
-    let options = TransformOptions::default();
-    let _ =
-        Transformer::new(&allocator, source_path, source_type, source_text, &ret.trivias, options)
-            .build(&mut program);
-    TestResult::Passed
+    let filename = source_path.file_name().unwrap().to_string_lossy();
+    let options = TransformOptions {
+        typescript: TypeScriptOptions::default(),
+        es2015: ES2015Options { arrow_function: Some(ArrowFunctionsOptions::default()) },
+        react: ReactOptions {
+            jsx_plugin: true,
+            jsx_self_plugin: true,
+            jsx_source_plugin: true,
+            ..Default::default()
+        },
+        ..Default::default()
+    };
+    let parse_result1 = Parser::new(&allocator, source_text, source_type).parse();
+    let mut program = parse_result1.program;
+    let _ = Transformer::new(
+        &allocator,
+        source_path,
+        source_type,
+        source_text,
+        &parse_result1.trivias,
+        options.clone(),
+    )
+    .build(&mut program);
+
+    let source_text1 =
+        Codegen::<false>::new(&filename, source_text, CodegenOptions::default(), None)
+            .build(&program)
+            .source_text;
+
+    let parse_result2 = Parser::new(&allocator, &source_text1, source_type).parse();
+    let mut program = parse_result2.program;
+
+    let _ = Transformer::new(
+        &allocator,
+        source_path,
+        source_type,
+        &source_text1,
+        &parse_result2.trivias,
+        options,
+    )
+    .build(&mut program);
+
+    let source_text2 =
+        Codegen::<false>::new(&filename, &source_text1, CodegenOptions::default(), None)
+            .build(&program)
+            .source_text;
+
+    let result = source_text1 == source_text2;
+
+    if result {
+        TestResult::Passed
+    } else {
+        TestResult::Mismatch(source_text1.clone(), source_text2)
+    }
 }
 
 pub struct TransformerTest262Case {
diff --git a/tasks/coverage/transformer_typescript.snap b/tasks/coverage/transformer_typescript.snap
index 2e813fa37..12d5fdd93 100644
--- a/tasks/coverage/transformer_typescript.snap
+++ b/tasks/coverage/transformer_typescript.snap
@@ -2,4 +2,14 @@ commit: 64d2eeea
 
 transformer_typescript Summary:
 AST Parsed     : 5243/5243 (100.00%)
-Positive Passed: 5243/5243 (100.00%)
+Positive Passed: 5233/5243 (99.81%)
+Mismatch: "compiler/elidedEmbeddedStatementsReplacedWithSemicolon.ts"
+Mismatch: "compiler/jsxComplexSignatureHasApplicabilityError.tsx"
+Mismatch: "compiler/jsxEmptyExpressionNotCountedAsChild.tsx"
+Mismatch: "compiler/sourceMapValidationClasses.ts"
+Mismatch: "compiler/styledComponentsInstantiaionLimitNotReached.ts"
+Mismatch: "compiler/tsxReactPropsInferenceSucceedsOnIntersections.tsx"
+Mismatch: "compiler/typeAliasDeclarationEmit3.ts"
+Mismatch: "conformance/classes/constructorDeclarations/superCalls/emitStatementsBeforeSuperCall.ts"
+Mismatch: "conformance/classes/constructorDeclarations/superCalls/emitStatementsBeforeSuperCallWithDefineFields.ts"
+Mismatch: "conformance/statements/VariableStatements/usingDeclarations/usingDeclarations.11.ts"