diff --git a/crates/oxc_transformer/examples/transformer.rs b/crates/oxc_transformer/examples/transformer.rs
index 0412ff0260498..13126ff2ccb62 100644
--- a/crates/oxc_transformer/examples/transformer.rs
+++ b/crates/oxc_transformer/examples/transformer.rs
@@ -24,11 +24,11 @@ fn main() {
     let ret = Parser::new(&allocator, &source_text, source_type).parse();
 
     if !ret.errors.is_empty() {
+        println!("Parser Errors:");
         for error in ret.errors {
             let error = error.with_source_code(source_text.clone());
             println!("{error:?}");
         }
-        return;
     }
 
     println!("Original:\n");
@@ -46,7 +46,7 @@ fn main() {
         },
         ..Default::default()
     };
-    Transformer::new(
+    let _ = Transformer::new(
         &allocator,
         path,
         source_type,
@@ -54,8 +54,7 @@ fn main() {
         ret.trivias.clone(),
         transform_options,
     )
-    .build(&mut program)
-    .unwrap();
+    .build(&mut program);
 
     let printed = Codegen::<false>::new("", &source_text, ret.trivias, CodegenOptions::default())
         .build(&program)
diff --git a/tasks/coverage/src/transformer.rs b/tasks/coverage/src/transformer.rs
index fdb76b19f0fd7..b5c97d58583b9 100644
--- a/tasks/coverage/src/transformer.rs
+++ b/tasks/coverage/src/transformer.rs
@@ -17,7 +17,7 @@ use crate::{
     typescript::TypeScriptCase,
 };
 
-/// Runs the transformer and make sure it doesn't crash.
+/// Idempotency test
 fn get_result(
     source_text: &str,
     source_type: SourceType,
@@ -27,76 +27,51 @@ fn get_result(
     let allocator = Allocator::default();
     let filename = source_path.file_name().unwrap().to_string_lossy();
     let options = options.unwrap_or_else(get_default_transformer_options);
-    let parse_result1 = Parser::new(&allocator, source_text, source_type).parse();
-    let mut program = parse_result1.program;
-    let transform_result1 = Transformer::new(
-        &allocator,
-        source_path,
-        source_type,
-        source_text,
-        parse_result1.trivias.clone(),
-        options.clone(),
-    )
-    .build(&mut program);
-
-    let ts_source_text1 = Codegen::<false>::new(
-        &filename,
-        source_text,
-        parse_result1.trivias.clone(),
-        CodegenOptions::default(),
-    )
-    .build(&program)
-    .source_text;
-
-    let source_text1 = Codegen::<false>::new(
-        &filename,
-        source_text,
-        parse_result1.trivias.clone(),
-        CodegenOptions::default(),
-    )
-    .build(&program)
-    .source_text;
-
-    if transform_result1.is_ok() && ts_source_text1 != source_text1 {
-        return TestResult::Mismatch(ts_source_text1.clone(), source_text1.clone());
-    }
-
-    let parse_result2 = Parser::new(&allocator, &ts_source_text1, source_type).parse();
-    let mut program = parse_result2.program;
-
-    let transform_result2 = Transformer::new(
-        &allocator,
-        source_path,
-        source_type,
-        &source_text1,
-        parse_result2.trivias.clone(),
-        options,
-    )
-    .build(&mut program);
-
-    let source_text2 = Codegen::<false>::new(
-        &filename,
-        &source_text1,
-        parse_result2.trivias,
-        CodegenOptions::default(),
-    )
-    .build(&program)
-    .source_text;
-
-    if source_text1 == source_text2
-        || transform_result1.is_err_and(|err| {
-            // If error messages are the same, we consider it as a pass.
-            transform_result2
-                .map_err(|err| err.iter().map(ToString::to_string).collect::<Vec<_>>().join("\n"))
-                .is_err_and(|err_message| {
-                    err.iter().map(ToString::to_string).collect::<Vec<_>>().join("\n")
-                        == err_message
-                })
-        })
-    {
+
+    // First pass
+    let transformed1 = {
+        let mut ret1 = Parser::new(&allocator, source_text, source_type).parse();
+        let _ = Transformer::new(
+            &allocator,
+            source_path,
+            source_type,
+            source_text,
+            ret1.trivias.clone(),
+            options.clone(),
+        )
+        .build(&mut ret1.program);
+        Codegen::<false>::new(
+            &filename,
+            source_text,
+            ret1.trivias.clone(),
+            CodegenOptions::default(),
+        )
+        .build(&ret1.program)
+        .source_text
+    };
+
+    // Second pass with only JavaScript parsing
+    let transformed2 = {
+        let source_type = SourceType::default().with_module(source_type.is_module());
+        let mut ret2 = Parser::new(&allocator, &transformed1, source_type).parse();
+        let _ = Transformer::new(
+            &allocator,
+            source_path,
+            source_type,
+            &transformed1,
+            ret2.trivias.clone(),
+            options,
+        )
+        .build(&mut ret2.program);
+        Codegen::<false>::new(&filename, source_text, ret2.trivias, CodegenOptions::default())
+            .build(&ret2.program)
+            .source_text
+    };
+
+    if transformed1 == transformed2 {
         TestResult::Passed
     } else {
-        TestResult::Mismatch(source_text1.clone(), source_text2)
+        TestResult::Mismatch(transformed1, transformed2)
     }
 }
 
diff --git a/tasks/coverage/transformer_babel.snap b/tasks/coverage/transformer_babel.snap
index cc33537346a44..6ddf3e86ec88c 100644
--- a/tasks/coverage/transformer_babel.snap
+++ b/tasks/coverage/transformer_babel.snap
@@ -2,4 +2,5 @@ commit: 12619ffe
 
 transformer_babel Summary:
 AST Parsed     : 2101/2101 (100.00%)
-Positive Passed: 2101/2101 (100.00%)
+Positive Passed: 2100/2101 (99.95%)
+Mismatch: "typescript/class/accessor/input.ts"
diff --git a/tasks/coverage/transformer_typescript.snap b/tasks/coverage/transformer_typescript.snap
index 1854ec204b948..268234062061b 100644
--- a/tasks/coverage/transformer_typescript.snap
+++ b/tasks/coverage/transformer_typescript.snap
@@ -2,5 +2,19 @@ commit: d8086f14
 
 transformer_typescript Summary:
 AST Parsed     : 5283/5283 (100.00%)
-Positive Passed: 5282/5283 (99.98%)
+Positive Passed: 5268/5283 (99.72%)
 Mismatch: "compiler/elidedEmbeddedStatementsReplacedWithSemicolon.ts"
+Mismatch: "compiler/esDecoratorsClassFieldsCrash.ts"
+Mismatch: "compiler/useBeforeDeclaration_classDecorators.2.ts"
+Mismatch: "conformance/classes/propertyMemberDeclarations/autoAccessor10.ts"
+Mismatch: "conformance/classes/propertyMemberDeclarations/autoAccessor2.ts"
+Mismatch: "conformance/classes/propertyMemberDeclarations/autoAccessor9.ts"
+Mismatch: "conformance/classes/propertyMemberDeclarations/autoAccessorAllowedModifiers.ts"
+Mismatch: "conformance/classes/propertyMemberDeclarations/staticAutoAccessors.ts"
+Mismatch: "conformance/classes/propertyMemberDeclarations/staticAutoAccessorsWithDecorators.ts"
+Mismatch: "conformance/decorators/legacyDecorators-contextualTypes.ts"
+Mismatch: "conformance/esDecorators/classDeclaration/classThisReference/esDecorators-classDeclaration-classThisReference.ts"
+Mismatch: "conformance/esDecorators/classDeclaration/fields/esDecorators-classDeclaration-fields-staticAccessor.ts"
+Mismatch: "conformance/esDecorators/classDeclaration/fields/esDecorators-classDeclaration-fields-staticPrivateAccessor.ts"
+Mismatch: "conformance/esDecorators/classExpression/esDecorators-classExpression-commentPreservation.ts"
+Mismatch: "conformance/esDecorators/esDecorators-contextualTypes.ts"