def METHOD_NAME(self):
    ProjectTransactionThresholdOverride.objects.create(
        project=self.project,
        organization=self.project.organization,
        threshold=300,
        metric=TransactionMetric.DURATION.value,
        transaction="fire",
    )
    MAX_TRANSACTION_THRESHOLDS_PER_PROJECT = 1
    with mock.patch(
        "sentry.api.endpoints.project_transaction_threshold_override.MAX_TRANSACTION_THRESHOLDS_PER_PROJECT",
        MAX_TRANSACTION_THRESHOLDS_PER_PROJECT,
    ):
        with self.feature(self.feature_name):
            response = self.client.post(
                self.url,
                data={
                    "transaction": self.data["transaction"],
                    "project": [self.project.id],
                    "metric": "duration",
                    "threshold": "600",
                },
            )
        assert response.status_code == 400
        assert response.data == {
            "non_field_errors": ["At most 1 configured transaction thresholds per project."]
        }