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diff --git a/tests/hipscat_import/data/malformed_catalogs/valid_truth/README b/tests/hipscat_import/data/malformed_catalogs/valid_truth/README
new file mode 100644
index 00000000..8dd3ea47
--- /dev/null
+++ b/tests/hipscat_import/data/malformed_catalogs/valid_truth/README
@@ -0,0 +1 @@
+small_sky_object_catalog
\ No newline at end of file
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diff --git a/tests/hipscat_import/verification/generate_malformed_catalogs.py b/tests/hipscat_import/verification/generate_malformed_catalogs.py
new file mode 100644
index 00000000..5809fd89
--- /dev/null
+++ b/tests/hipscat_import/verification/generate_malformed_catalogs.py
@@ -0,0 +1,229 @@
+import random
+import shutil
+from pathlib import Path
+
+import attrs
+import pyarrow
+import pyarrow.dataset
+import pyarrow.parquet
+
+DATA_DIR = Path(__file__).parent.parent.parent.parent / "tests/hipscat_import/data"
+VALID_CATALOG_DIR = DATA_DIR / "small_sky_object_catalog"
+MALFORMED_CATALOGS_DIR = DATA_DIR / "malformed_catalogs"
+
+
+def run(
+    valid_catalog_dir: Path = VALID_CATALOG_DIR, malformed_catalogs_dir: Path = MALFORMED_CATALOGS_DIR
+) -> None:
+    """Generate malformed catalogs to be used as test data for verification.
+    This only needs to be run once unless/until it is desirable to regenerate the dataset.
+    """
+    Generate.run(valid_catalog_dir=valid_catalog_dir, malformed_catalogs_dir=malformed_catalogs_dir)
+
+
+@attrs.define
+class ValidBase:
+    dataset: pyarrow.dataset.Dataset = attrs.field()
+    frag: pyarrow.dataset.FileFragment = attrs.field()
+    tbl: pyarrow.Table = attrs.field()
+    schema: pyarrow.Schema = attrs.field()
+    valid_catalog_dir: Path = attrs.field()
+    malformed_catalogs_dir: Path = attrs.field()
+    insert_dir: str = attrs.field(factory=str)
+
+    @classmethod
+    def from_dirs(cls, valid_catalog_dir: Path, malformed_catalogs_dir: Path) -> "ValidBase":
+        valid_ds = pyarrow.dataset.parquet_dataset(valid_catalog_dir / "_metadata")
+        valid_frag = next(valid_ds.get_fragments())
+        valid_tbl = valid_frag.to_table()
+        return cls(
+            dataset=valid_ds,
+            frag=valid_frag,
+            tbl=valid_tbl,
+            schema=valid_tbl.schema,
+            valid_catalog_dir=valid_catalog_dir,
+            malformed_catalogs_dir=malformed_catalogs_dir,
+        )
+
+    @property
+    def fmeta(self) -> Path:
+        return self.malformed_catalogs_dir / self.insert_dir / "_metadata"
+
+    @property
+    def fcmeta(self) -> Path:
+        return self.malformed_catalogs_dir / self.insert_dir / "_common_metadata"
+
+    @property
+    def fdata(self) -> Path:
+        frag_key = Path(self.frag.path).relative_to(self.valid_catalog_dir)
+        return self.malformed_catalogs_dir / self.insert_dir / frag_key
+
+
+@attrs.define
+class Generate:
+    def run(
+        self,
+        valid_catalog_dir: Path = VALID_CATALOG_DIR,
+        malformed_catalogs_dir: Path = MALFORMED_CATALOGS_DIR,
+    ) -> None:
+        """Generate malformed catalogs to be used as test data for verification.
+        This only needs to be run once unless/until it is desirable to regenerate the dataset.
+        """
+        if malformed_catalogs_dir.is_dir():
+            print(f"Output directory exists. Remove it and try again.\n{malformed_catalogs_dir}")
+            return
+        print(f"Generating malformed catalogs from valid catalog at {valid_catalog_dir}...")
+
+        valid = ValidBase.from_dirs(
+            valid_catalog_dir=valid_catalog_dir, malformed_catalogs_dir=malformed_catalogs_dir
+        )
+        generate = Generate()
+        generate.valid_truth(valid)
+        generate.bad_schemas(valid)
+        generate.no_rowgroup_stats(valid)
+        generate.wrong_files_and_rows(valid)
+
+    def malformed(self, valid: ValidBase) -> None:
+        """Case: <TEMPLATE>"""
+        valid.insert_dir = ""
+        self._start_new_catalog(valid)
+        self._collect_and_write_metadata(valid)
+        print(f"Invalid catalog written to {valid.fmeta.parent}")
+
+    def bad_schemas(self, valid: ValidBase) -> None:
+        """Case: Files are altered in a way that affects the schema after _metadata gets written."""
+        valid.insert_dir = "bad_schemas"
+        self._start_new_catalog(valid)
+
+        # Write new files with the correct schema
+        fextra_col = valid.fdata.with_suffix(".extra_column.parquet")
+        fmissing_col = valid.fdata.with_suffix(".missing_column.parquet")
+        fno_metadata = valid.fdata.with_suffix(".no_metadata.parquet")
+        fwrong_types = valid.fdata.with_suffix(".wrong_dtypes.parquet")
+        for _fout in [fmissing_col, fextra_col, fwrong_types]:
+            pyarrow.parquet.write_table(valid.tbl, _fout)
+
+        # Write a _metadata that is correct except for missing file-level metadata
+        self._collect_and_write_metadata(valid, schema=valid.schema.remove_metadata())
+
+        # Overwrite the new files using incorrect schemas.
+        # drop the file-level metadata
+        pyarrow.parquet.write_table(valid.tbl.replace_schema_metadata(None), fno_metadata)
+        # drop a column
+        pyarrow.parquet.write_table(valid.tbl.drop_columns("dec_error"), fmissing_col)
+        # add an extra column
+        extra_col = pyarrow.array(random.sample(range(1000), len(valid.tbl)))
+        extra_col_tbl = valid.tbl.add_column(5, pyarrow.field("extra", pyarrow.int64()), extra_col)
+        pyarrow.parquet.write_table(extra_col_tbl, fextra_col)
+        # change some types
+        wrong_dtypes = [
+            fld if not fld.name.startswith("ra") else fld.with_type(pyarrow.float16()) for fld in valid.schema
+        ]
+        wrong_dtypes_schema = pyarrow.schema(wrong_dtypes).with_metadata(valid.schema.metadata)
+        pyarrow.parquet.write_table(valid.tbl.cast(wrong_dtypes_schema), fwrong_types)
+
+        # Write a _common_metadata with the wrong dtypes.
+        pyarrow.parquet.write_metadata(schema=wrong_dtypes_schema, where=valid.fcmeta)
+
+        # Write a _common_metadata with custom metadata and no hipscat columns.
+        # This mimics a schema that could have been passed as 'use_schema_file' upon import.
+        fcustom_md = valid.fcmeta.with_suffix(".import")
+        hipscat_cols = ["_hipscat_index", "Norder", "Dir", "Npix"]
+        import_fields = [fld for fld in valid.schema if not fld.name in hipscat_cols]
+        import_schema = pyarrow.schema(import_fields).with_metadata({b"custom_key": b"custom_value"})
+        pyarrow.parquet.write_metadata(schema=import_schema, where=fcustom_md)
+
+        print(f"Invalid catalog written to {valid.fmeta.parent}")
+
+    def no_rowgroup_stats(self, valid: ValidBase) -> None:
+        """Case: ."""
+        valid.insert_dir = "no_rowgroup_stats"
+        self._start_new_catalog(valid)
+        # drop the row group statistics
+        pyarrow.parquet.write_table(valid.tbl, valid.fdata, write_statistics=False)
+        self._collect_and_write_metadata(valid)
+        print(f"Invalid catalog written to {valid.fmeta.parent}")
+
+    def valid_truth(self, valid: ValidBase) -> None:
+        """Case: This is the valid catalog that we start with and will be used as the expected truth during testing."""
+        valid.insert_dir = "valid_truth"
+        base_dir = valid.fmeta.parent
+        base_dir.mkdir(parents=True)
+
+        # write a README pointing to the valid_catalog_dir used to generate malformed datasets
+        with open(base_dir / "README", "w") as fout:
+            fout.writelines(str(valid.valid_catalog_dir.relative_to(DATA_DIR)))
+
+        print(f"Valid, truth README written to {base_dir}")
+
+    def wrong_files_and_rows(self, valid: ValidBase) -> None:
+        """Case: ."""
+        valid.insert_dir = "wrong_files_and_rows"
+        self._start_new_catalog(valid)
+
+        fmissing_file = valid.fdata.with_suffix(".missing_file.parquet")
+        fextra_file = valid.fdata.with_suffix(".extra_file.parquet")
+        fextra_rows = valid.fdata.with_suffix(".extra_rows.parquet")
+
+        pyarrow.parquet.write_table(valid.tbl, fmissing_file)
+        pyarrow.parquet.write_table(valid.tbl, fextra_rows)
+        self._collect_and_write_metadata(valid)
+
+        fmissing_file.unlink()
+        pyarrow.parquet.write_table(valid.tbl, fextra_file)
+        pyarrow.parquet.write_table(self._tbl_with_extra_rows(valid), fextra_rows)
+
+        print(f"Invalid catalog written to {valid.fmeta.parent}")
+
+    def _tbl_with_extra_rows(self, valid: ValidBase) -> pyarrow.Table:
+        """Generate a table with extra rows."""
+        # generate new rows
+        rng = range(len(valid.tbl))
+        nrows, new_rows = 2, {}
+        for col in valid.tbl.column_names:
+            if col not in ("_hipscat_index", "id"):
+                # just take a random sample
+                new_rows[col] = valid.tbl.column(col).take(random.sample(rng, nrows))
+            else:
+                # increment the max value to avoid duplicates
+                max_id = valid.tbl.column(col).sort()[-1].as_py()
+                new_rows[col] = [i + max_id for i in range(1, nrows + 1)]
+
+        # add the rows to the table
+        new_tbl = pyarrow.concat_tables([valid.tbl, pyarrow.Table.from_pydict(new_rows, schema=valid.schema)])
+        return new_tbl
+
+    @staticmethod
+    def _start_new_catalog(valid: ValidBase, with_ancillaries: bool = False) -> None:
+        # Start a new catalog by creating the directory and copying in valid files.
+        valid.fdata.parent.mkdir(parents=True)
+        shutil.copy(valid.frag.path, valid.fdata)
+
+        root_files = valid.valid_catalog_dir.iterdir()
+        if not with_ancillaries:
+            root_files = [fin for fin in root_files if fin.name.endswith("metadata")]
+        for fin in root_files:
+            if fin.is_file():
+                shutil.copy(fin, valid.malformed_catalogs_dir / valid.insert_dir / fin.name)
+
+    @staticmethod
+    def _collect_and_write_metadata(valid: ValidBase, schema: pyarrow.Schema | None = None) -> None:
+        base_dir = valid.fmeta.parent
+        schema = schema or valid.schema
+        ignore_prefixes = [
+            ".",
+            "_",
+            "catalog_info.json",
+            "partition_info.csv",
+            "point_map.fits",
+            "provenance_info.json",
+        ]
+        dataset = pyarrow.dataset.dataset(base_dir, ignore_prefixes=ignore_prefixes)
+        metadata_collector = []
+        for frag in dataset.get_fragments():
+            frag.ensure_complete_metadata()
+            frag.metadata.set_file_path(str(Path(frag.path).relative_to(base_dir)))
+            metadata_collector.append(frag.metadata)
+        pyarrow.parquet.write_metadata(
+            schema=schema, where=valid.fmeta, metadata_collector=metadata_collector
+        )