diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index 49686a6..47a2356 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -160,3 +160,29 @@ jobs:
         working-directory: ./betterproto2
         shell: bash
         run: uv run poe test
+
+      # Run conformance test on all Ubuntu and MacOS versions
+      - name: Install Node.js
+        if: matrix.os == 'Ubuntu' || matrix.os == 'MacOS'
+        uses: actions/setup-node@v6
+        with:
+          node-version: 24
+
+      - name: Install conformance runner
+        if: matrix.os == 'Ubuntu' || matrix.os == 'MacOS'
+        run: npm install -g protobuf-conformance@33.1.0
+
+      - name: Create test script
+        if: matrix.os == 'Ubuntu' || matrix.os == 'MacOS'
+        shell: bash
+        working-directory: ./betterproto2
+        run: |
+          echo '#!/bin/bash' > script.sh
+          echo 'python -m tests.conformance.main' >> script.sh
+          chmod +x script.sh
+
+      - name: Run conformance tests
+        if: matrix.os == 'Ubuntu' || matrix.os == 'MacOS'
+        working-directory: ./betterproto2
+        run: |
+          uv run conformance_test_runner --failure_list tests/conformance/failing_tests.txt ./script.sh
diff --git a/betterproto2/tests/conformance/failing_tests.txt b/betterproto2/tests/conformance/failing_tests.txt
new file mode 100644
index 0000000..0142ca0
--- /dev/null
+++ b/betterproto2/tests/conformance/failing_tests.txt
@@ -0,0 +1,174 @@
+Required.Proto3.DurationProtoInputTooLarge.JsonOutput # Should have failed to serialize, but didn't.
+Required.Proto3.DurationProtoInputTooSmall.JsonOutput # Should have failed to serialize, but didn't.
+Required.Proto3.DurationProtoNanosTooLarge.JsonOutput # Should have failed to serialize, but didn't.
+Required.Proto3.DurationProtoNanosTooSmall.JsonOutput # Should have failed to serialize, but didn't.
+Required.Proto3.DurationProtoNanosWrongSign.JsonOutput # Should have failed to serialize, but didn't.
+Required.Proto3.DurationProtoNanosWrongSignNegativeSecs.JsonOutput # Should have failed to serialize, but didn't.
+Required.Proto3.JsonInput.AnyWithFieldMask.JsonOutput # Failed to parse input or produce output.
+Required.Proto3.JsonInput.AnyWithFieldMask.ProtobufOutput # Failed to parse input or produce output.
+Required.Proto3.JsonInput.AnyWithNoType.JsonOutput # Failed to parse input or produce output.
+Required.Proto3.JsonInput.AnyWithNoType.ProtobufOutput # Failed to parse input or produce output.
+Required.Proto3.JsonInput.BoolMapEscapedKey.ProtobufOutput # Failed to parse input or produce output.
+Required.Proto3.JsonInput.BoolMapField.ProtobufOutput # Failed to parse input or produce output.
+Required.Proto3.JsonInput.DoubleFieldTooLarge # Should have failed to parse, but didn't.
+Required.Proto3.JsonInput.DoubleFieldTooSmall # Should have failed to parse, but didn't.
+Required.Proto3.JsonInput.DurationJsonInputTooLarge # Should have failed to parse, but didn't.
+Required.Proto3.JsonInput.DurationMaxValue.JsonOutput # JSON output we received from test was unparseable.
+Required.Proto3.JsonInput.DurationMaxValue.ProtobufOutput # Output was not equivalent to reference message: modified: optional_duration.seconds: 315576000000 -> 315576000001deleted: option
+Required.Proto3.JsonInput.DurationMinValue.JsonOutput # Failed to parse input or produce output.
+Required.Proto3.JsonInput.DurationMinValue.ProtobufOutput # Failed to parse input or produce output.
+Required.Proto3.JsonInput.DurationNegativeNanos.JsonOutput # Failed to parse input or produce output.
+Required.Proto3.JsonInput.DurationNegativeNanos.ProtobufOutput # Failed to parse input or produce output.
+Required.Proto3.JsonInput.DurationNegativeSeconds.JsonOutput # Failed to parse input or produce output.
+Required.Proto3.JsonInput.DurationNegativeSeconds.ProtobufOutput # Failed to parse input or produce output.
+Required.Proto3.JsonInput.DurationRepeatedValue.JsonOutput # Failed to parse input or produce output.
+Required.Proto3.JsonInput.DurationRepeatedValue.ProtobufOutput # Failed to parse input or produce output.
+Required.Proto3.JsonInput.EmptyFieldMask.JsonOutput # Failed to parse input or produce output.
+Required.Proto3.JsonInput.EmptyFieldMask.ProtobufOutput # Failed to parse input or produce output.
+Required.Proto3.JsonInput.FieldMask.JsonOutput # Failed to parse input or produce output.
+Required.Proto3.JsonInput.FieldMask.ProtobufOutput # Failed to parse input or produce output.
+Required.Proto3.JsonInput.FieldNameInLowerCamelCase.Validator # Expected JSON payload but got type 1
+Required.Proto3.JsonInput.FieldNameInSnakeCase.JsonOutput # Failed to parse input or produce output.
+Required.Proto3.JsonInput.FieldNameInSnakeCase.ProtobufOutput # Failed to parse input or produce output.
+Required.Proto3.JsonInput.FieldNameWithMixedCases.JsonOutput # Failed to parse input or produce output.
+Required.Proto3.JsonInput.FieldNameWithMixedCases.ProtobufOutput # Failed to parse input or produce output.
+Required.Proto3.JsonInput.FieldNameWithMixedCases.Validator # Expected JSON payload but got type 1
+Required.Proto3.JsonInput.FieldNameWithNumbers.JsonOutput # Failed to parse input or produce output.
+Required.Proto3.JsonInput.FieldNameWithNumbers.ProtobufOutput # Failed to parse input or produce output.
+Required.Proto3.JsonInput.FieldNameWithNumbers.Validator # Expected JSON payload but got type 1
+Required.Proto3.JsonInput.FloatFieldTooLarge # Should have failed to parse, but didn't.
+Required.Proto3.JsonInput.FloatFieldTooSmall # Should have failed to parse, but didn't.
+Required.Proto3.JsonInput.Int32FieldLeadingSpace # Should have failed to parse, but didn't.
+Required.Proto3.JsonInput.Int32FieldNotInteger # Should have failed to parse, but didn't.
+Required.Proto3.JsonInput.Int32FieldQuotedExponentialValue.JsonOutput # Failed to parse input or produce output.
+Required.Proto3.JsonInput.Int32FieldQuotedExponentialValue.ProtobufOutput # Failed to parse input or produce output.
+Required.Proto3.JsonInput.Int32FieldTooLarge # Should have failed to parse, but didn't.
+Required.Proto3.JsonInput.Int32FieldTooSmall # Should have failed to parse, but didn't.
+Required.Proto3.JsonInput.Int32FieldTrailingSpace # Should have failed to parse, but didn't.
+Required.Proto3.JsonInput.Int64FieldTooLarge # Should have failed to parse, but didn't.
+Required.Proto3.JsonInput.Int64FieldTooSmall # Should have failed to parse, but didn't.
+Required.Proto3.JsonInput.OneofFieldDuplicate # Should have failed to parse, but didn't.
+Required.Proto3.JsonInput.OptionalBytesWrapper.ProtobufOutput # Failed to parse input or produce output.
+Required.Proto3.JsonInput.OptionalWrapperTypesWithNonDefaultValue.ProtobufOutput # Failed to parse input or produce output.
+Required.Proto3.JsonInput.OriginalProtoFieldName.JsonOutput # Failed to parse input or produce output.
+Required.Proto3.JsonInput.OriginalProtoFieldName.ProtobufOutput # Failed to parse input or produce output.
+Required.Proto3.JsonInput.RepeatedBytesWrapper.ProtobufOutput # Failed to parse input or produce output.
+Required.Proto3.JsonInput.RepeatedFieldWrongElementTypeExpectingIntegersGotBool # Should have failed to parse, but didn't.
+Required.Proto3.JsonInput.RepeatedFieldWrongElementTypeExpectingStringsGotBool # Should have failed to parse, but didn't.
+Required.Proto3.JsonInput.RepeatedFieldWrongElementTypeExpectingStringsGotInt # Should have failed to parse, but didn't.
+Required.Proto3.JsonInput.RepeatedFieldWrongElementTypeExpectingStringsGotMessage # Should have failed to parse, but didn't.
+Required.Proto3.JsonInput.SkipsDefaultPrimitive.Validator # Expected JSON payload but got type 1
+Required.Proto3.JsonInput.StringFieldNotAString # Should have failed to parse, but didn't.
+Required.Proto3.JsonInput.TimestampJsonInputLowercaseT # Should have failed to parse, but didn't.
+Required.Proto3.JsonInput.TimestampJsonInputLowercaseZ # Should have failed to parse, but didn't.
+Required.Proto3.JsonInput.TimestampJsonInputMissingT # Should have failed to parse, but didn't.
+Required.Proto3.JsonInput.TimestampLittleAfterEpochlValue.JsonOutput # Output was not equivalent to reference message: deleted: optional_timestamp.nanos: 1
+Required.Proto3.JsonInput.TimestampLittleAfterEpochlValue.ProtobufOutput # Output was not equivalent to reference message: deleted: optional_timestamp.nanos: 1
+Required.Proto3.JsonInput.TimestampLittleBeforeEpochValue.JsonOutput # Output was not equivalent to reference message: modified: optional_timestamp.nanos: 999999999 -> 999999000
+Required.Proto3.JsonInput.TimestampLittleBeforeEpochValue.ProtobufOutput # Output was not equivalent to reference message: modified: optional_timestamp.nanos: 999999999 -> 999999000
+Required.Proto3.JsonInput.TimestampMaxValue.JsonOutput # Output was not equivalent to reference message: modified: optional_timestamp.nanos: 999999999 -> 999999000
+Required.Proto3.JsonInput.TimestampMaxValue.ProtobufOutput # Output was not equivalent to reference message: modified: optional_timestamp.nanos: 999999999 -> 999999000
+Required.Proto3.JsonInput.TimestampNanoAfterEpochlValue.JsonOutput # Output was not equivalent to reference message: deleted: optional_timestamp.nanos: 1
+Required.Proto3.JsonInput.TimestampNanoAfterEpochlValue.ProtobufOutput # Output was not equivalent to reference message: deleted: optional_timestamp.nanos: 1
+Required.Proto3.JsonInput.TimestampNanoBeforeEpochValue.JsonOutput # Output was not equivalent to reference message: modified: optional_timestamp.nanos: 999999999 -> 999999000
+Required.Proto3.JsonInput.TimestampNanoBeforeEpochValue.ProtobufOutput # Output was not equivalent to reference message: modified: optional_timestamp.nanos: 999999999 -> 999999000
+Required.Proto3.JsonInput.TimestampRepeatedValue.JsonOutput # Output was not equivalent to reference message: modified: repeated_timestamp[1].nanos: 999999999 -> 999999000
+Required.Proto3.JsonInput.TimestampRepeatedValue.ProtobufOutput # Output was not equivalent to reference message: modified: repeated_timestamp[1].nanos: 999999999 -> 999999000
+Required.Proto3.JsonInput.TimestampWithMissingColonInOffset # Should have failed to parse, but didn't.
+Required.Proto3.JsonInput.Uint32FieldNotInteger # Should have failed to parse, but didn't.
+Required.Proto3.JsonInput.Uint32FieldTooLarge # Should have failed to parse, but didn't.
+Required.Proto3.JsonInput.Uint64FieldTooLarge # Should have failed to parse, but didn't.
+Required.Proto3.ProtobufInput.IllegalZeroFieldNum_Case_0 # Should have failed to parse, but didn't.
+Required.Proto3.ProtobufInput.IllegalZeroFieldNum_Case_1 # Should have failed to parse, but didn't.
+Required.Proto3.ProtobufInput.IllegalZeroFieldNum_Case_2 # Should have failed to parse, but didn't.
+Required.Proto3.ProtobufInput.IllegalZeroFieldNum_Case_3 # Should have failed to parse, but didn't.
+Required.Proto3.ProtobufInput.MismatchedGroupTags # Should have failed to parse, but didn't.
+Required.Proto3.ProtobufInput.MismatchedNestedGroupTags # Should have failed to parse, but didn't.
+Required.Proto3.ProtobufInput.PrematureEofBeforeUnknownValue.DOUBLE # Should have failed to parse, but didn't.
+Required.Proto3.ProtobufInput.PrematureEofBeforeUnknownValue.FIXED32 # Should have failed to parse, but didn't.
+Required.Proto3.ProtobufInput.PrematureEofBeforeUnknownValue.FIXED64 # Should have failed to parse, but didn't.
+Required.Proto3.ProtobufInput.PrematureEofBeforeUnknownValue.FLOAT # Should have failed to parse, but didn't.
+Required.Proto3.ProtobufInput.PrematureEofBeforeUnknownValue.SFIXED32 # Should have failed to parse, but didn't.
+Required.Proto3.ProtobufInput.PrematureEofBeforeUnknownValue.SFIXED64 # Should have failed to parse, but didn't.
+Required.Proto3.ProtobufInput.PrematureEofInDelimitedDataForKnownNonRepeatedValue.BYTES # Should have failed to parse, but didn't.
+Required.Proto3.ProtobufInput.PrematureEofInDelimitedDataForKnownNonRepeatedValue.MESSAGE # Should have failed to parse, but didn't.
+Required.Proto3.ProtobufInput.PrematureEofInDelimitedDataForKnownNonRepeatedValue.STRING # Should have failed to parse, but didn't.
+Required.Proto3.ProtobufInput.PrematureEofInDelimitedDataForKnownRepeatedValue.BYTES # Should have failed to parse, but didn't.
+Required.Proto3.ProtobufInput.PrematureEofInDelimitedDataForKnownRepeatedValue.MESSAGE # Should have failed to parse, but didn't.
+Required.Proto3.ProtobufInput.PrematureEofInDelimitedDataForKnownRepeatedValue.STRING # Should have failed to parse, but didn't.
+Required.Proto3.ProtobufInput.PrematureEofInDelimitedDataForUnknownValue.BYTES # Should have failed to parse, but didn't.
+Required.Proto3.ProtobufInput.PrematureEofInDelimitedDataForUnknownValue.MESSAGE # Should have failed to parse, but didn't.
+Required.Proto3.ProtobufInput.PrematureEofInDelimitedDataForUnknownValue.STRING # Should have failed to parse, but didn't.
+Required.Proto3.ProtobufInput.PrematureEofInPackedField.BOOL # Should have failed to parse, but didn't.
+Required.Proto3.ProtobufInput.PrematureEofInPackedField.DOUBLE # Should have failed to parse, but didn't.
+Required.Proto3.ProtobufInput.PrematureEofInPackedField.ENUM # Should have failed to parse, but didn't.
+Required.Proto3.ProtobufInput.PrematureEofInPackedField.FIXED32 # Should have failed to parse, but didn't.
+Required.Proto3.ProtobufInput.PrematureEofInPackedField.FIXED64 # Should have failed to parse, but didn't.
+Required.Proto3.ProtobufInput.PrematureEofInPackedField.FLOAT # Should have failed to parse, but didn't.
+Required.Proto3.ProtobufInput.PrematureEofInPackedField.INT32 # Should have failed to parse, but didn't.
+Required.Proto3.ProtobufInput.PrematureEofInPackedField.INT64 # Should have failed to parse, but didn't.
+Required.Proto3.ProtobufInput.PrematureEofInPackedField.SFIXED32 # Should have failed to parse, but didn't.
+Required.Proto3.ProtobufInput.PrematureEofInPackedField.SFIXED64 # Should have failed to parse, but didn't.
+Required.Proto3.ProtobufInput.PrematureEofInPackedField.SINT32 # Should have failed to parse, but didn't.
+Required.Proto3.ProtobufInput.PrematureEofInPackedField.SINT64 # Should have failed to parse, but didn't.
+Required.Proto3.ProtobufInput.PrematureEofInPackedField.UINT32 # Should have failed to parse, but didn't.
+Required.Proto3.ProtobufInput.PrematureEofInPackedField.UINT64 # Should have failed to parse, but didn't.
+Required.Proto3.ProtobufInput.PrematureEofInsideUnknownValue.DOUBLE # Should have failed to parse, but didn't.
+Required.Proto3.ProtobufInput.PrematureEofInsideUnknownValue.FIXED32 # Should have failed to parse, but didn't.
+Required.Proto3.ProtobufInput.PrematureEofInsideUnknownValue.FIXED64 # Should have failed to parse, but didn't.
+Required.Proto3.ProtobufInput.PrematureEofInsideUnknownValue.FLOAT # Should have failed to parse, but didn't.
+Required.Proto3.ProtobufInput.PrematureEofInsideUnknownValue.SFIXED32 # Should have failed to parse, but didn't.
+Required.Proto3.ProtobufInput.PrematureEofInsideUnknownValue.SFIXED64 # Should have failed to parse, but didn't.
+Required.Proto3.ProtobufInput.RepeatedScalarMessageMerge.JsonOutput # Output was not equivalent to reference message: deleted: optional_nested_message.corecursive.optional_int64: 1234modified: optio
+Required.Proto3.ProtobufInput.RepeatedScalarMessageMerge.ProtobufOutput # Output was not equivalent to reference message: deleted: optional_nested_message.corecursive.optional_int64: 1234modified: optio
+Required.Proto3.ProtobufInput.RepeatedScalarSelectsLast.ENUM.JsonOutput # JSON output we received from test was unparseable.
+Required.Proto3.ProtobufInput.UnknownWireType6_Field0_Version1 # Should have failed to parse, but didn't.
+Required.Proto3.ProtobufInput.UnknownWireType6_Field0_Version3 # Should have failed to parse, but didn't.
+Required.Proto3.ProtobufInput.UnknownWireType6_Field1_Version1 # Should have failed to parse, but didn't.
+Required.Proto3.ProtobufInput.UnknownWireType6_Field1_Version3 # Should have failed to parse, but didn't.
+Required.Proto3.ProtobufInput.UnknownWireType6_Field2_Version1 # Should have failed to parse, but didn't.
+Required.Proto3.ProtobufInput.UnknownWireType6_Field2_Version3 # Should have failed to parse, but didn't.
+Required.Proto3.ProtobufInput.UnknownWireType6_Field3_Version1 # Should have failed to parse, but didn't.
+Required.Proto3.ProtobufInput.UnknownWireType6_Field3_Version3 # Should have failed to parse, but didn't.
+Required.Proto3.ProtobufInput.UnknownWireType7_Field0_Version1 # Should have failed to parse, but didn't.
+Required.Proto3.ProtobufInput.UnknownWireType7_Field0_Version3 # Should have failed to parse, but didn't.
+Required.Proto3.ProtobufInput.UnknownWireType7_Field1_Version1 # Should have failed to parse, but didn't.
+Required.Proto3.ProtobufInput.UnknownWireType7_Field1_Version3 # Should have failed to parse, but didn't.
+Required.Proto3.ProtobufInput.UnknownWireType7_Field2_Version1 # Should have failed to parse, but didn't.
+Required.Proto3.ProtobufInput.UnknownWireType7_Field2_Version3 # Should have failed to parse, but didn't.
+Required.Proto3.ProtobufInput.UnknownWireType7_Field3_Version1 # Should have failed to parse, but didn't.
+Required.Proto3.ProtobufInput.UnknownWireType7_Field3_Version3 # Should have failed to parse, but didn't.
+Required.Proto3.ProtobufInput.UnmatchedEndGroup # Should have failed to parse, but didn't.
+Required.Proto3.ProtobufInput.UnmatchedEndGroupNested # Should have failed to parse, but didn't.
+Required.Proto3.ProtobufInput.UnmatchedEndGroupNestedLen # Should have failed to parse, but didn't.
+Required.Proto3.ProtobufInput.UnmatchedEndGroupUnknown # Should have failed to parse, but didn't.
+Required.Proto3.ProtobufInput.UnmatchedEndGroupWithData # Should have failed to parse, but didn't.
+Required.Proto3.ProtobufInput.UnmatchedEndGroupWrongType # Should have failed to parse, but didn't.
+Required.Proto3.ProtobufInput.UnmatchedStartGroup # Should have failed to parse, but didn't.
+Required.Proto3.ProtobufInput.UnmatchedStartGroupNested # Should have failed to parse, but didn't.
+Required.Proto3.ProtobufInput.UnmatchedStartGroupNestedLen # Should have failed to parse, but didn't.
+Required.Proto3.ProtobufInput.UnmatchedStartGroupUnknown # Should have failed to parse, but didn't.
+Required.Proto3.ProtobufInput.UnmatchedStartGroupWithData # Should have failed to parse, but didn't.
+Required.Proto3.ProtobufInput.UnmatchedStartGroupWrongType # Should have failed to parse, but didn't.
+Required.Proto3.ProtobufInput.ValidDataMap.STRING.MESSAGE.MissingDefault.JsonOutput # Failed to parse input or produce output.
+Required.Proto3.ProtobufInput.ValidDataMap.STRING.MESSAGE.MissingDefault.ProtobufOutput # Failed to parse input or produce output.
+Required.Proto3.ProtobufInput.ValidDataOneof.BOOL.MultipleValuesForDifferentField.JsonOutput # JSON output we received from test was unparseable.
+Required.Proto3.ProtobufInput.ValidDataOneof.BYTES.MultipleValuesForDifferentField.JsonOutput # JSON output we received from test was unparseable.
+Required.Proto3.ProtobufInput.ValidDataOneof.DOUBLE.MultipleValuesForDifferentField.JsonOutput # JSON output we received from test was unparseable.
+Required.Proto3.ProtobufInput.ValidDataOneof.ENUM.MultipleValuesForDifferentField.JsonOutput # JSON output we received from test was unparseable.
+Required.Proto3.ProtobufInput.ValidDataOneof.FLOAT.MultipleValuesForDifferentField.JsonOutput # JSON output we received from test was unparseable.
+Required.Proto3.ProtobufInput.ValidDataOneof.MESSAGE.Merge.JsonOutput # Output was not equivalent to reference message: deleted: oneof_nested_message.corecursive.optional_int32: 1deleted: oneof_nested
+Required.Proto3.ProtobufInput.ValidDataOneof.MESSAGE.Merge.ProtobufOutput # Output was not equivalent to reference message: deleted: oneof_nested_message.corecursive.optional_int32: 1deleted: oneof_nested
+Required.Proto3.ProtobufInput.ValidDataOneof.MESSAGE.MultipleValuesForDifferentField.JsonOutput # JSON output we received from test was unparseable.
+Required.Proto3.ProtobufInput.ValidDataOneof.STRING.MultipleValuesForDifferentField.JsonOutput # JSON output we received from test was unparseable.
+Required.Proto3.ProtobufInput.ValidDataOneof.UINT32.MultipleValuesForDifferentField.JsonOutput # JSON output we received from test was unparseable.
+Required.Proto3.ProtobufInput.ValidDataOneof.UINT32.MultipleValuesForDifferentField.ProtobufOutput # Output was not equivalent to reference message: deleted: oneof_uint32: 1added: oneof_nested_message: { }
+Required.Proto3.ProtobufInput.ValidDataOneof.UINT64.MultipleValuesForDifferentField.JsonOutput # JSON output we received from test was unparseable.
+Required.Proto3.ProtobufInput.ValidDataRepeated.ENUM.PackedInput.JsonOutput # JSON output we received from test was unparseable.
+Required.Proto3.ProtobufInput.ValidDataRepeated.ENUM.UnpackedInput.JsonOutput # JSON output we received from test was unparseable.
+Required.Proto3.ProtobufInput.ValidDataScalar.ENUM[4].JsonOutput # JSON output we received from test was unparseable.
+Required.Proto3.ProtobufInput.ValidDataScalar.ENUM[5].JsonOutput # JSON output we received from test was unparseable.
+Required.Proto3.TimestampProtoInputTooLarge.JsonOutput # Should have failed to serialize, but didn't.
+Required.Proto3.TimestampProtoInputTooSmall.JsonOutput # Should have failed to serialize, but didn't.
+Required.Proto3.TimestampProtoNanoTooLarge.JsonOutput # Should have failed to serialize, but didn't.
+Required.Proto3.TimestampProtoNegativeNanos.JsonOutput # Should have failed to serialize, but didn't.
diff --git a/betterproto2/tests/conformance/main.py b/betterproto2/tests/conformance/main.py
new file mode 100644
index 0000000..57d09ac
--- /dev/null
+++ b/betterproto2/tests/conformance/main.py
@@ -0,0 +1,119 @@
+import struct
+import sys
+
+import betterproto2
+from tests.outputs.conformance.conformance import (
+    ConformanceRequest,
+    ConformanceResponse,
+    TestCategory,
+    WireFormat,
+)
+from tests.outputs.conformance.protobuf_test_messages.proto3 import TestAllTypesProto3
+
+test_count = 0
+verbose = False
+
+
+class ProtocolError(Exception):
+    pass
+
+
+def do_test(request: ConformanceRequest) -> ConformanceResponse:
+    response = ConformanceResponse()
+
+    # is_json = betterproto2.which_one_of(request, "payload")[0] == "json_payload"
+
+    if request.message_type != "protobuf_test_messages.proto3.TestAllTypesProto3":
+        return ConformanceResponse(skipped="non proto3 tests not supported")
+
+    try:
+        if betterproto2.which_one_of(request, "payload")[0] == "protobuf_payload":
+            try:
+                test_message = TestAllTypesProto3.parse(request.protobuf_payload)
+            except Exception as e:
+                response.parse_error = str(e)
+                return response
+
+        elif betterproto2.which_one_of(request, "payload")[0] == "json_payload":
+            try:
+                ignore_unknown_fields = request.test_category == TestCategory.JSON_IGNORE_UNKNOWN_PARSING_TEST
+                test_message = TestAllTypesProto3.from_json(
+                    request.json_payload, ignore_unknown_fields=ignore_unknown_fields
+                )
+            except Exception as e:
+                response.parse_error = str(e)
+                return response
+
+        elif betterproto2.which_one_of(request, "payload")[0] == "text_payload":
+            return ConformanceResponse(skipped="text input not supported")
+
+        else:
+            raise ProtocolError("Request didn't have payload.")
+
+        if request.requested_output_format == WireFormat.UNSPECIFIED:
+            raise ProtocolError("Unspecified output format")
+
+        elif request.requested_output_format == WireFormat.PROTOBUF:
+            response.protobuf_payload = bytes(test_message)
+
+        elif request.requested_output_format == WireFormat.JSON:
+            try:
+                response.json_payload = test_message.to_json()
+            except Exception as e:
+                response.serialize_error = str(e)
+                return response
+
+        elif request.requested_output_format == WireFormat.TEXT_FORMAT:
+            return ConformanceResponse(skipped="text output not supported")
+            # response.text_payload = text_format.MessageToString(
+            #     test_message, print_unknown_fields=request.print_unknown_fields
+            # )
+
+    except Exception as e:
+        response.runtime_error = str(e)
+
+    return response
+
+
+def do_test_io():
+    length_bytes = sys.stdin.buffer.read(4)
+    if len(length_bytes) == 0:
+        return False  # EOF
+    elif len(length_bytes) != 4:
+        raise OSError("I/O error")
+
+    length = struct.unpack("<I", length_bytes)[0]
+    serialized_request = sys.stdin.buffer.read(length)
+    if len(serialized_request) != length:
+        raise OSError("I/O error")
+
+    request = ConformanceRequest.parse(serialized_request)
+
+    response = do_test(request)
+
+    serialized_response = bytes(response)
+    sys.stdout.buffer.write(struct.pack("<I", len(serialized_response)))
+    sys.stdout.buffer.write(serialized_response)
+    sys.stdout.buffer.flush()
+
+    # if verbose:
+    #   sys.stderr.write(
+    #       "conformance_python: request=%s, response=%s\n"
+    #       % (
+    #           request.ShortDebugString().c_str(),
+    #           response.ShortDebugString().c_str(),
+    #       )
+    #   )
+
+    global test_count
+    test_count += 1
+
+    return True
+
+
+while True:
+    if not do_test_io():
+        print(
+            "conformance_python: received EOF from test runner after", test_count, "tests, exiting\n", file=sys.stderr
+        )
+        sys.exit(0)
diff --git a/betterproto2_compiler/tests/generate.py b/betterproto2_compiler/tests/generate.py
index b0ebd66..e2a05d8 100644
--- a/betterproto2_compiler/tests/generate.py
+++ b/betterproto2_compiler/tests/generate.py
@@ -75,6 +75,7 @@ async def main_async():
         generate_test("casing", semaphore, reference=True),
         generate_test("casing", semaphore),
         generate_test("compiler_lib", semaphore),
+        generate_test("conformance", semaphore),
         generate_test("deprecated", semaphore, reference=True),
         generate_test("deprecated", semaphore, client_generation="async"),
         generate_test("documentation", semaphore, client_generation="async"),
diff --git a/betterproto2_compiler/tests/inputs/conformance/conformance.proto b/betterproto2_compiler/tests/inputs/conformance/conformance.proto
new file mode 100644
index 0000000..bbb7554
--- /dev/null
+++ b/betterproto2_compiler/tests/inputs/conformance/conformance.proto
@@ -0,0 +1,172 @@
+// Protocol Buffers - Google's data interchange format
+// Copyright 2008 Google Inc.  All rights reserved.
+//
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file or at
+// https://developers.google.com/open-source/licenses/bsd
+
+syntax = "proto3";
+
+package conformance;
+
+option java_package = "com.google.protobuf.conformance";
+option objc_class_prefix = "Conformance";
+
+// This defines the conformance testing protocol.  This protocol exists between
+// the conformance test suite itself and the code being tested.  For each test,
+// the suite will send a ConformanceRequest message and expect a
+// ConformanceResponse message.
+//
+// You can either run the tests in two different ways:
+//
+//   1. in-process (using the interface in conformance_test.h).
+//
+//   2. as a sub-process communicating over a pipe.  Information about how to
+//      do this is in conformance_test_runner.cc.
+//
+// Pros/cons of the two approaches:
+//
+//   - running as a sub-process is much simpler for languages other than C/C++.
+//
+//   - running as a sub-process may be more tricky in unusual environments like
+//     iOS apps, where fork/stdin/stdout are not available.
+
+enum WireFormat {
+  UNSPECIFIED = 0;
+  PROTOBUF = 1;
+  JSON = 2;
+  JSPB = 3; // Only used inside Google. Opensource testees just skip it.
+  TEXT_FORMAT = 4;
+}
+
+enum TestCategory {
+  UNSPECIFIED_TEST = 0;
+  BINARY_TEST = 1; // Test binary wire format.
+  JSON_TEST = 2; // Test json wire format.
+  // Similar to JSON_TEST. However, during parsing json, testee should ignore
+  // unknown fields. This feature is optional. Each implementation can decide
+  // whether to support it.  See
+  // https://developers.google.com/protocol-buffers/docs/proto3#json_options
+  // for more detail.
+  JSON_IGNORE_UNKNOWN_PARSING_TEST = 3;
+  // Test jspb wire format. Only used inside Google. Opensource testees just
+  // skip it.
+  JSPB_TEST = 4;
+  // Test text format. For cpp, java and python, testees can already deal with
+  // this type. Testees of other languages can simply skip it.
+  TEXT_FORMAT_TEST = 5;
+}
+
+// Meant to encapsulate all types of tests: successes, skips, failures, etc.
+// Therefore, this may or may not have a failure message. Failure messages
+// may be truncated for our failure lists.
+message TestStatus {
+  string name = 1;
+  string failure_message = 2;
+  // What an actual test name matched to in a failure list. Can be wildcarded or
+  // an exact match without wildcards.
+  string matched_name = 3;
+}
+
+// The conformance runner will request a list of failures as the first request.
+// This will be known by message_type == "conformance.FailureSet", a conformance
+// test should return a serialized FailureSet in protobuf_payload.
+message FailureSet {
+  repeated TestStatus test = 2;
+  reserved 1;
+}
+
+// Represents a single test case's input.  The testee should:
+//
+//   1. parse this proto (which should always succeed)
+//   2. parse the protobuf or JSON payload in "payload" (which may fail)
+//   3. if the parse succeeded, serialize the message in the requested format.
+message ConformanceRequest {
+  // The payload (whether protobuf of JSON) is always for a
+  // protobuf_test_messages.proto3.TestAllTypes proto (as defined in
+  // src/google/protobuf/proto3_test_messages.proto).
+  oneof payload {
+    bytes protobuf_payload = 1;
+    string json_payload = 2;
+    // Only used inside Google.  Opensource testees just skip it.
+    string jspb_payload = 7;
+    string text_payload = 8;
+  }
+
+  // Which format should the testee serialize its message to?
+  WireFormat requested_output_format = 3;
+
+  // The full name for the test message to use; for the moment, either:
+  // protobuf_test_messages.proto3.TestAllTypesProto3 or
+  // protobuf_test_messages.proto2.TestAllTypesProto2 or
+  // protobuf_test_messages.editions.proto2.TestAllTypesProto2 or
+  // protobuf_test_messages.editions.proto3.TestAllTypesProto3 or
+  // protobuf_test_messages.editions.TestAllTypesEdition2023.
+  string message_type = 4;
+
+  // Each test is given a specific test category. Some category may need
+  // specific support in testee programs. Refer to the definition of
+  // TestCategory for more information.
+  TestCategory test_category = 5;
+
+  // Specify details for how to encode jspb.
+  JspbEncodingConfig jspb_encoding_options = 6;
+
+  // This can be used in json and text format. If true, testee should print
+  // unknown fields instead of ignore. This feature is optional.
+  bool print_unknown_fields = 9;
+}
+
+// Represents a single test case's output.
+message ConformanceResponse {
+  oneof result {
+    // This string should be set to indicate parsing failed.  The string can
+    // provide more information about the parse error if it is available.
+    //
+    // Setting this string does not necessarily mean the testee failed the
+    // test.  Some of the test cases are intentionally invalid input.
+    string parse_error = 1;
+
+    // If the input was successfully parsed but errors occurred when
+    // serializing it to the requested output format, set the error message in
+    // this field.
+    string serialize_error = 6;
+
+    // This should be set if the test program timed out.  The string should
+    // provide more information about what the child process was doing when it
+    // was killed.
+    string timeout_error = 9;
+
+    // This should be set if some other error occurred.  This will always
+    // indicate that the test failed.  The string can provide more information
+    // about the failure.
+    string runtime_error = 2;
+
+    // If the input was successfully parsed and the requested output was
+    // protobuf, serialize it to protobuf and set it in this field.
+    bytes protobuf_payload = 3;
+
+    // If the input was successfully parsed and the requested output was JSON,
+    // serialize to JSON and set it in this field.
+    string json_payload = 4;
+
+    // For when the testee skipped the test, likely because a certain feature
+    // wasn't supported, like JSON input/output.
+    string skipped = 5;
+
+    // If the input was successfully parsed and the requested output was JSPB,
+    // serialize to JSPB and set it in this field. JSPB is only used inside
+    // Google. Opensource testees can just skip it.
+    string jspb_payload = 7;
+
+    // If the input was successfully parsed and the requested output was
+    // TEXT_FORMAT, serialize to TEXT_FORMAT and set it in this field.
+    string text_payload = 8;
+  }
+}
+
+// Encoding options for jspb format.
+message JspbEncodingConfig {
+  // Encode the value field of Any as jspb array if true, otherwise binary.
+  bool use_jspb_array_any_format = 1;
+}
diff --git a/betterproto2_compiler/tests/inputs/conformance/test_messages_proto3.proto b/betterproto2_compiler/tests/inputs/conformance/test_messages_proto3.proto
new file mode 100644
index 0000000..088e1ea
--- /dev/null
+++ b/betterproto2_compiler/tests/inputs/conformance/test_messages_proto3.proto
@@ -0,0 +1,267 @@
+// Protocol Buffers - Google's data interchange format
+// Copyright 2008 Google Inc.  All rights reserved.
+//
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file or at
+// https://developers.google.com/open-source/licenses/bsd
+//
+// Test schema for proto3 messages.  This test schema is used by:
+//
+// - benchmarks
+// - fuzz tests
+// - conformance tests
+//
+
+syntax = "proto3";
+
+package protobuf_test_messages.proto3;
+
+import "google/protobuf/any.proto";
+import "google/protobuf/duration.proto";
+import "google/protobuf/field_mask.proto";
+import "google/protobuf/struct.proto";
+import "google/protobuf/timestamp.proto";
+import "google/protobuf/wrappers.proto";
+
+option cc_enable_arenas = true;
+option java_package = "com.google.protobuf_test_messages.proto3";
+option objc_class_prefix = "Proto3";
+// This is the default, but we specify it here explicitly.
+option optimize_for = SPEED;
+
+// This proto includes every type of field in both singular and repeated
+// forms.
+//
+// Also, crucially, all messages and enums in this file are eventually
+// submessages of this message.  So for example, a fuzz test of TestAllTypes
+// could trigger bugs that occur in any message type in this file.  We verify
+// this stays true in a unit test.
+message TestAllTypesProto3 {
+  message NestedMessage {
+    int32 a = 1;
+    TestAllTypesProto3 corecursive = 2;
+  }
+
+  enum NestedEnum {
+    FOO = 0;
+    BAR = 1;
+    BAZ = 2;
+    NEG = -1; // Intentionally negative.
+  }
+
+  enum AliasedEnum {
+    option allow_alias = true;
+
+    ALIAS_FOO = 0;
+    ALIAS_BAR = 1;
+    ALIAS_BAZ = 2;
+    MOO = 2;
+    moo = 2;
+    bAz = 2;
+  }
+
+  // Singular
+  // test [kotlin] comment
+  int32 optional_int32 = 1;
+  int64 optional_int64 = 2;
+  uint32 optional_uint32 = 3;
+  uint64 optional_uint64 = 4;
+  sint32 optional_sint32 = 5;
+  sint64 optional_sint64 = 6;
+  fixed32 optional_fixed32 = 7;
+  fixed64 optional_fixed64 = 8;
+  sfixed32 optional_sfixed32 = 9;
+  sfixed64 optional_sfixed64 = 10;
+  float optional_float = 11;
+  double optional_double = 12;
+  bool optional_bool = 13;
+  string optional_string = 14;
+  bytes optional_bytes = 15;
+
+  NestedMessage optional_nested_message = 18;
+  ForeignMessage optional_foreign_message = 19;
+
+  NestedEnum optional_nested_enum = 21;
+  ForeignEnum optional_foreign_enum = 22;
+  AliasedEnum optional_aliased_enum = 23;
+
+  string optional_string_piece = 24 [ctype = STRING_PIECE];
+  string optional_cord = 25 [ctype = CORD];
+
+  TestAllTypesProto3 recursive_message = 27;
+
+  // Repeated
+  repeated int32 repeated_int32 = 31;
+  repeated int64 repeated_int64 = 32;
+  repeated uint32 repeated_uint32 = 33;
+  repeated uint64 repeated_uint64 = 34;
+  repeated sint32 repeated_sint32 = 35;
+  repeated sint64 repeated_sint64 = 36;
+  repeated fixed32 repeated_fixed32 = 37;
+  repeated fixed64 repeated_fixed64 = 38;
+  repeated sfixed32 repeated_sfixed32 = 39;
+  repeated sfixed64 repeated_sfixed64 = 40;
+  repeated float repeated_float = 41;
+  repeated double repeated_double = 42;
+  repeated bool repeated_bool = 43;
+  repeated string repeated_string = 44;
+  repeated bytes repeated_bytes = 45;
+
+  repeated NestedMessage repeated_nested_message = 48;
+  repeated ForeignMessage repeated_foreign_message = 49;
+
+  repeated NestedEnum repeated_nested_enum = 51;
+  repeated ForeignEnum repeated_foreign_enum = 52;
+
+  repeated string repeated_string_piece = 54 [ctype = STRING_PIECE];
+  repeated string repeated_cord = 55 [ctype = CORD];
+
+  // Packed
+  repeated int32 packed_int32 = 75 [packed = true];
+  repeated int64 packed_int64 = 76 [packed = true];
+  repeated uint32 packed_uint32 = 77 [packed = true];
+  repeated uint64 packed_uint64 = 78 [packed = true];
+  repeated sint32 packed_sint32 = 79 [packed = true];
+  repeated sint64 packed_sint64 = 80 [packed = true];
+  repeated fixed32 packed_fixed32 = 81 [packed = true];
+  repeated fixed64 packed_fixed64 = 82 [packed = true];
+  repeated sfixed32 packed_sfixed32 = 83 [packed = true];
+  repeated sfixed64 packed_sfixed64 = 84 [packed = true];
+  repeated float packed_float = 85 [packed = true];
+  repeated double packed_double = 86 [packed = true];
+  repeated bool packed_bool = 87 [packed = true];
+  repeated NestedEnum packed_nested_enum = 88 [packed = true];
+
+  // Unpacked
+  repeated int32 unpacked_int32 = 89 [packed = false];
+  repeated int64 unpacked_int64 = 90 [packed = false];
+  repeated uint32 unpacked_uint32 = 91 [packed = false];
+  repeated uint64 unpacked_uint64 = 92 [packed = false];
+  repeated sint32 unpacked_sint32 = 93 [packed = false];
+  repeated sint64 unpacked_sint64 = 94 [packed = false];
+  repeated fixed32 unpacked_fixed32 = 95 [packed = false];
+  repeated fixed64 unpacked_fixed64 = 96 [packed = false];
+  repeated sfixed32 unpacked_sfixed32 = 97 [packed = false];
+  repeated sfixed64 unpacked_sfixed64 = 98 [packed = false];
+  repeated float unpacked_float = 99 [packed = false];
+  repeated double unpacked_double = 100 [packed = false];
+  repeated bool unpacked_bool = 101 [packed = false];
+  repeated NestedEnum unpacked_nested_enum = 102 [packed = false];
+
+  // Map
+  map<int32, int32> map_int32_int32 = 56;
+  map<int64, int64> map_int64_int64 = 57;
+  map<uint32, uint32> map_uint32_uint32 = 58;
+  map<uint64, uint64> map_uint64_uint64 = 59;
+  map<sint32, sint32> map_sint32_sint32 = 60;
+  map<sint64, sint64> map_sint64_sint64 = 61;
+  map<fixed32, fixed32> map_fixed32_fixed32 = 62;
+  map<fixed64, fixed64> map_fixed64_fixed64 = 63;
+  map<sfixed32, sfixed32> map_sfixed32_sfixed32 = 64;
+  map<sfixed64, sfixed64> map_sfixed64_sfixed64 = 65;
+  map<int32, float> map_int32_float = 66;
+  map<int32, double> map_int32_double = 67;
+  map<bool, bool> map_bool_bool = 68;
+  map<string, string> map_string_string = 69;
+  map<string, bytes> map_string_bytes = 70;
+  map<string, NestedMessage> map_string_nested_message = 71;
+  map<string, ForeignMessage> map_string_foreign_message = 72;
+  map<string, NestedEnum> map_string_nested_enum = 73;
+  map<string, ForeignEnum> map_string_foreign_enum = 74;
+
+  oneof oneof_field {
+    uint32 oneof_uint32 = 111;
+    NestedMessage oneof_nested_message = 112;
+    string oneof_string = 113;
+    bytes oneof_bytes = 114;
+    bool oneof_bool = 115;
+    uint64 oneof_uint64 = 116;
+    float oneof_float = 117;
+    double oneof_double = 118;
+    NestedEnum oneof_enum = 119;
+    google.protobuf.NullValue oneof_null_value = 120;
+  }
+
+  // Well-known types
+  google.protobuf.BoolValue optional_bool_wrapper = 201;
+  google.protobuf.Int32Value optional_int32_wrapper = 202;
+  google.protobuf.Int64Value optional_int64_wrapper = 203;
+  google.protobuf.UInt32Value optional_uint32_wrapper = 204;
+  google.protobuf.UInt64Value optional_uint64_wrapper = 205;
+  google.protobuf.FloatValue optional_float_wrapper = 206;
+  google.protobuf.DoubleValue optional_double_wrapper = 207;
+  google.protobuf.StringValue optional_string_wrapper = 208;
+  google.protobuf.BytesValue optional_bytes_wrapper = 209;
+
+  repeated google.protobuf.BoolValue repeated_bool_wrapper = 211;
+  repeated google.protobuf.Int32Value repeated_int32_wrapper = 212;
+  repeated google.protobuf.Int64Value repeated_int64_wrapper = 213;
+  repeated google.protobuf.UInt32Value repeated_uint32_wrapper = 214;
+  repeated google.protobuf.UInt64Value repeated_uint64_wrapper = 215;
+  repeated google.protobuf.FloatValue repeated_float_wrapper = 216;
+  repeated google.protobuf.DoubleValue repeated_double_wrapper = 217;
+  repeated google.protobuf.StringValue repeated_string_wrapper = 218;
+  repeated google.protobuf.BytesValue repeated_bytes_wrapper = 219;
+
+  google.protobuf.Duration optional_duration = 301;
+  google.protobuf.Timestamp optional_timestamp = 302;
+  google.protobuf.FieldMask optional_field_mask = 303;
+  google.protobuf.Struct optional_struct = 304;
+  google.protobuf.Any optional_any = 305;
+  google.protobuf.Value optional_value = 306;
+  google.protobuf.NullValue optional_null_value = 307;
+
+  repeated google.protobuf.Duration repeated_duration = 311;
+  repeated google.protobuf.Timestamp repeated_timestamp = 312;
+  repeated google.protobuf.FieldMask repeated_fieldmask = 313;
+  repeated google.protobuf.Struct repeated_struct = 324;
+  repeated google.protobuf.Any repeated_any = 315;
+  repeated google.protobuf.Value repeated_value = 316;
+  repeated google.protobuf.ListValue repeated_list_value = 317;
+
+  // Test field-name-to-JSON-name convention.
+  // (protobuf says names can be any valid C/C++ identifier.)
+  int32 fieldname1 = 401;
+  int32 field_name2 = 402;
+  int32 _field_name3 = 403;
+  int32 field__name4_ = 404;
+  int32 field0name5 = 405;
+  int32 field_0_name6 = 406;
+  int32 fieldName7 = 407;
+  int32 FieldName8 = 408;
+  int32 field_Name9 = 409;
+  int32 Field_Name10 = 410;
+  int32 FIELD_NAME11 = 411;
+  int32 FIELD_name12 = 412;
+  int32 __field_name13 = 413;
+  int32 __Field_name14 = 414;
+  int32 field__name15 = 415;
+  int32 field__Name16 = 416;
+  int32 field_name17__ = 417;
+  int32 Field_name18__ = 418;
+
+  // Reserved for testing unknown fields
+  reserved 501 to 510;
+
+  reserved "reserved_field";
+  reserved 999999;
+}
+
+message ForeignMessage {
+  int32 c = 1;
+}
+
+enum ForeignEnum {
+  FOREIGN_FOO = 0;
+  FOREIGN_BAR = 1;
+  FOREIGN_BAZ = 2;
+}
+
+message NullHypothesisProto3 {}
+
+message EnumOnlyProto3 {
+  enum Bool {
+    kFalse = 0;
+    kTrue = 1;
+  }
+}