diff --git a/tests/unit/conftest.py b/tests/unit/conftest.py
index a3c42f9f8e8..b06dd39981e 100644
--- a/tests/unit/conftest.py
+++ b/tests/unit/conftest.py
@@ -5,6 +5,7 @@
 from dbt.contracts.graph.nodes import SourceDefinition
 
 # All manifest related fixtures.
+from tests.unit.utils.adapter import *  # noqa
 from tests.unit.utils.manifest import *  # noqa
 from tests.unit.utils.project import *  # noqa
 
diff --git a/tests/unit/parser/test_manifest.py b/tests/unit/parser/test_manifest.py
index 9a84414a99e..b7d470a3552 100644
--- a/tests/unit/parser/test_manifest.py
+++ b/tests/unit/parser/test_manifest.py
@@ -2,25 +2,14 @@
 from unittest.mock import MagicMock, patch
 
 import pytest
+from pytest_mock import MockerFixture
 
 from dbt.config import RuntimeConfig
 from dbt.contracts.graph.manifest import Manifest
 from dbt.flags import set_from_args
 from dbt.parser.manifest import ManifestLoader
-
-
-@pytest.fixture
-def mock_project():
-    mock_project = MagicMock(RuntimeConfig)
-    mock_project.cli_vars = {}
-    mock_project.args = MagicMock()
-    mock_project.args.profile = "test"
-    mock_project.args.target = "test"
-    mock_project.project_env_vars = {}
-    mock_project.profile_env_vars = {}
-    mock_project.project_target_path = "mock_target_path"
-    mock_project.credentials = MagicMock()
-    return mock_project
+from dbt.parser.read_files import FileDiff
+from dbt.tracking import User
 
 
 class TestPartialParse:
@@ -91,3 +80,84 @@ def test_partial_parse_safe_update_project_parser_files_partially(
         assert "full_reparse_reason" in exc_info
         assert "KeyError: 'Whoopsie!'" == exc_info["exception"]
         assert isinstance(exc_info["code"], str) or isinstance(exc_info["code"], type(None))
+
+
+class TestGetFullManifest:
+    @pytest.fixture
+    def set_required_mocks(
+        self, mocker: MockerFixture, manifest: Manifest, mock_adapter: MagicMock
+    ):
+        mocker.patch("dbt.parser.manifest.get_adapter").return_value = mock_adapter
+        mocker.patch("dbt.parser.manifest.ManifestLoader.load").return_value = manifest
+        mocker.patch("dbt.parser.manifest._check_manifest").return_value = None
+        mocker.patch(
+            "dbt.parser.manifest.ManifestLoader.save_macros_to_adapter"
+        ).return_value = None
+        mocker.patch("dbt.tracking.active_user").return_value = User(None)
+
+    def test_write_perf_info(
+        self,
+        mock_project: MagicMock,
+        mocker: MockerFixture,
+        set_required_mocks,
+    ) -> None:
+        write_perf_info = mocker.patch("dbt.parser.manifest.ManifestLoader.write_perf_info")
+
+        ManifestLoader.get_full_manifest(
+            config=mock_project,
+            # write_perf_info=False let it default instead
+        )
+        assert not write_perf_info.called
+
+        ManifestLoader.get_full_manifest(config=mock_project, write_perf_info=False)
+        assert not write_perf_info.called
+
+        ManifestLoader.get_full_manifest(config=mock_project, write_perf_info=True)
+        assert write_perf_info.called
+
+    def test_reset(
+        self,
+        mock_project: MagicMock,
+        mock_adapter: MagicMock,
+        set_required_mocks,
+    ) -> None:
+
+        ManifestLoader.get_full_manifest(
+            config=mock_project,
+            # reset=False let it default instead
+        )
+        assert not mock_project.clear_dependencies.called
+        assert not mock_adapter.clear_macro_resolver.called
+
+        ManifestLoader.get_full_manifest(config=mock_project, reset=False)
+        assert not mock_project.clear_dependencies.called
+        assert not mock_adapter.clear_macro_resolver.called
+
+        ManifestLoader.get_full_manifest(config=mock_project, reset=True)
+        assert mock_project.clear_dependencies.called
+        assert mock_adapter.clear_macro_resolver.called
+
+    def test_partial_parse_file_diff_flag(
+        self,
+        mock_project: MagicMock,
+        mocker: MockerFixture,
+        set_required_mocks,
+    ) -> None:
+
+        # FileDiff.from_dict is only called if PARTIAL_PARSE_FILE_DIFF == False
+        # So we can track this function call to check if setting PARTIAL_PARSE_FILE_DIFF
+        # works appropriately
+        mock_file_diff = mocker.patch("dbt.parser.read_files.FileDiff.from_dict")
+        mock_file_diff.return_value = FileDiff([], [], [])
+
+        set_from_args(Namespace(), {})
+        ManifestLoader.get_full_manifest(config=mock_project)
+        assert not mock_file_diff.called
+
+        set_from_args(Namespace(PARTIAL_PARSE_FILE_DIFF=True), {})
+        ManifestLoader.get_full_manifest(config=mock_project)
+        assert not mock_file_diff.called
+
+        set_from_args(Namespace(PARTIAL_PARSE_FILE_DIFF=False), {})
+        ManifestLoader.get_full_manifest(config=mock_project)
+        assert mock_file_diff.called
diff --git a/tests/unit/utils/adapter.py b/tests/unit/utils/adapter.py
new file mode 100644
index 00000000000..06555b0e400
--- /dev/null
+++ b/tests/unit/utils/adapter.py
@@ -0,0 +1,21 @@
+from unittest.mock import MagicMock
+
+import pytest
+
+from dbt.adapters.postgres import PostgresAdapter
+from dbt.adapters.sql import SQLConnectionManager
+
+
+@pytest.fixture
+def mock_connection_manager() -> MagicMock:
+    mock_connection_manager = MagicMock(SQLConnectionManager)
+    mock_connection_manager.set_query_header = lambda query_header_context: None
+    return mock_connection_manager
+
+
+@pytest.fixture
+def mock_adapter(mock_connection_manager: MagicMock) -> MagicMock:
+    mock_adapter = MagicMock(PostgresAdapter)
+    mock_adapter.connections = mock_connection_manager
+    mock_adapter.clear_macro_resolver = MagicMock()
+    return mock_adapter
diff --git a/tests/unit/utils/project.py b/tests/unit/utils/project.py
index b34e03da494..c7215990e6d 100644
--- a/tests/unit/utils/project.py
+++ b/tests/unit/utils/project.py
@@ -1,6 +1,9 @@
+from unittest.mock import MagicMock
+
 import pytest
 
 from dbt.adapters.contracts.connection import QueryComment
+from dbt.config import RuntimeConfig
 from dbt.config.project import Project, RenderComponents, VarProvider
 from dbt.config.selectors import SelectorConfig
 from dbt.contracts.project import PackageConfig
@@ -68,3 +71,18 @@ def project(selector_config: SelectorConfig) -> Project:
         restrict_access=False,
         dbt_cloud={},
     )
+
+
+@pytest.fixture
+def mock_project():
+    mock_project = MagicMock(RuntimeConfig)
+    mock_project.cli_vars = {}
+    mock_project.args = MagicMock()
+    mock_project.args.profile = "test"
+    mock_project.args.target = "test"
+    mock_project.project_env_vars = {}
+    mock_project.profile_env_vars = {}
+    mock_project.project_target_path = "mock_target_path"
+    mock_project.credentials = MagicMock()
+    mock_project.clear_dependencies = MagicMock()
+    return mock_project