diff --git a/tests/__init__.py b/tests/__init__.py
new file mode 100644
index 0000000..e69de29
diff --git a/tests/test_bigquery_metadata.py b/tests/test_bigquery_metadata.py
new file mode 100644
index 0000000..0c4908f
--- /dev/null
+++ b/tests/test_bigquery_metadata.py
@@ -0,0 +1,171 @@
+import pytest
+from attr import dataclass
+from funcy import partial
+from google.cloud.bigquery import (
+    ExternalConfig,
+    SourceFormat,
+    TimePartitioning,
+    TimePartitioningType,
+)
+from odd_collector_sdk.utils.metadata import DefinitionType, extract_metadata
+from pydantic import BaseModel
+
+from odd_collector_gcp.adapters.bigquery_storage.mapper import BigQueryMetadataEncoder
+
+
+@pytest.fixture
+def partial_extract_metadata():
+    return partial(
+        extract_metadata,
+        datasource="test_datasource",
+        definition=DefinitionType.DATASET,
+    )
+
+
+GCS_URI = "gs://path-to-your-data-in-gcs/*.csv"
+external_config = ExternalConfig(SourceFormat.CSV)
+external_config.source_uris = [GCS_URI]
+time_partitioning = TimePartitioning(type_=TimePartitioningType.DAY)
+
+COMPLEX_METADATA = {
+    "meta": "meta",
+    "nested_meta": {
+        "nested_field_one": 1,
+        "nested_field_two": "string",
+        "nested_field_three": [{"foo": "bat"}, {"foo": {}}],
+        "nested_field_four": {
+            "more_nested_field": 1,
+            "more_nested_field_two": {},
+            "more_nested_field_three": "string",
+            "more_nested_field_external": external_config,
+            "more_nested_field_time_partitioning": time_partitioning,
+        },
+        "nested_field_five": {},
+        "nested_field_external": external_config,
+        "nested_field_time_partitioning": time_partitioning,
+    },
+}
+
+FLATTEN = {
+    "meta": "meta",
+    "nested_meta.nested_field_one": 1,
+    "nested_meta.nested_field_two": "string",
+    "nested_meta.nested_field_three": [{"foo": "bat"}, {"foo": {}}],
+    "nested_meta.nested_field_four.more_nested_field": 1,
+    "nested_meta.nested_field_four.more_nested_field_two": {},
+    "nested_meta.nested_field_four.more_nested_field_three": "string",
+    "nested_meta.nested_field_four.more_nested_field_external": external_config,
+    "nested_meta.nested_field_four.more_nested_field_time_partitioning": time_partitioning,
+    "nested_meta.nested_field_five": {},
+    "nested_field_external": external_config,
+    "nested_field_time_partitioning": time_partitioning,
+}
+
+ENCODED_METADATA = {
+    "meta": "meta",
+    "nested_meta": {
+        "nested_field_one": 1,
+        "nested_field_two": "string",
+        "nested_field_three": [{"foo": "bat"}, {"foo": {}}],
+        "nested_field_four": {
+            "more_nested_field": 1,
+            "more_nested_field_two": {},
+            "more_nested_field_three": "string",
+            "more_nested_field_external": {
+                "csv_options": {},
+                "options": {},
+                "schema": [],
+                "source_format": "CSV",
+                "source_uris": ["gs://path-to-your-data-in-gcs/*.csv"],
+            },
+            "more_nested_field_time_partitioning": {"type_": "DAY"},
+        },
+        "nested_field_five": {},
+        "nested_field_external": {
+            "csv_options": {},
+            "options": {},
+            "schema": [],
+            "source_format": "CSV",
+            "source_uris": ["gs://path-to-your-data-in-gcs/*.csv"],
+        },
+        "nested_field_time_partitioning": {"type_": "DAY"},
+    },
+}
+
+FLATTEN_ENCODED_METADATA = {
+    "meta": "meta",
+    "nested_meta.nested_field_one": 1,
+    "nested_meta.nested_field_two": "string",
+    "nested_meta.nested_field_three": [{"foo": "bat"}, {"foo": {}}],
+    "nested_meta.nested_field_four.more_nested_field": 1,
+    "nested_meta.nested_field_four.more_nested_field_two": {},
+    "nested_meta.nested_field_four.more_nested_field_three": "string",
+    "nested_meta.nested_field_four.more_nested_field_external.csv_options": {},
+    "nested_meta.nested_field_four.more_nested_field_external.options": {},
+    "nested_meta.nested_field_four.more_nested_field_external.schema": [],
+    "nested_meta.nested_field_four.more_nested_field_external.source_format": "CSV",
+    "nested_meta.nested_field_four.more_nested_field_external.source_uris": [
+        "gs://path-to-your-data-in-gcs/*.csv"
+    ],
+    "nested_meta.nested_field_four.more_nested_field_time_partitioning.type_": "DAY",
+    "nested_meta.nested_field_five": {},
+    "nested_field_external.csv_options": {},
+    "nested_field_external.options": {},
+    "nested_field_external.schema": [],
+    "nested_field_external.source_format": "CSV",
+    "nested_field_external.source_uris": ["gs://path-to-your-data-in-gcs/*.csv"],
+    "nested_field_time_partitioning.type_": "DAY",
+}
+
+
+class Entity:
+    def __init__(self, foo, bar):
+        self.foo = foo
+        self.bar = bar
+
+
+class EntityWithMetadata:
+    def __init__(self, foo, bar, odd_metadata):
+        self.foo = foo
+        self.bar = bar
+        self.odd_metadata = odd_metadata
+
+
+@dataclass
+class DataclassEntity:
+    foo: str
+    bar: str
+
+
+@dataclass
+class DataclassEntityWithMetadata:
+    foo: str
+    bar: str
+    odd_metadata: dict
+
+
+class PydanticEntity(BaseModel):
+    foo: str
+    bar: str
+
+
+class PydanticEntityWithMetadata(BaseModel):
+    foo: str
+    bar: str
+    odd_metadata: dict
+
+
+def test_nested_complex_types(partial_extract_metadata):
+    entity = EntityWithMetadata(foo="foo", bar="bar", odd_metadata=COMPLEX_METADATA)
+    metadata = partial_extract_metadata(
+        entity=entity, jsonify=True, json_encoder=BigQueryMetadataEncoder
+    )
+    assert metadata.metadata == ENCODED_METADATA
+
+
+def test_nested_flatten_complex_types(partial_extract_metadata):
+    entity = EntityWithMetadata(foo="foo", bar="bar", odd_metadata=FLATTEN)
+    metadata = partial_extract_metadata(
+        entity=entity, jsonify=True, flatten=True, json_encoder=BigQueryMetadataEncoder
+    )
+    assert metadata.metadata == FLATTEN_ENCODED_METADATA