test(compare): add basic integration tests

CHANGELOG.md

@@ -7,6 +7,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 ## [Unreleased]
 ### Added
 - Support for `dbt==1.9`. [#85]
+- Integration tests for `compare`. [#84]
 
 ### Changed
 - Refactor tests. [#86]

dbt_coverage/__init__.py

@@ -782,7 +782,7 @@ def compute_coverage(catalog: Catalog, cov_type: CoverageType):
     return coverage_report
 
 
-def compare_reports(report, compare_report):
+def compare_reports(report: CoverageReport, compare_report: CoverageReport) -> CoverageDiff:
     diff = CoverageDiff(compare_report, report)
 
     print(diff.summary())
@@ -869,11 +869,18 @@ def do_compute(
     return coverage_report
 
 
-def do_compare(report: Path, compare_report: Path):
+def do_compare(report: Path, compare_report: Path) -> CoverageDiff:
     """
     Compares two coverage reports generated by the ``compute`` command.
 
     Use this method in your Python code to bypass typer.
+
+    Args:
+        report: ``Path`` to the current report - the after state.
+        compare_report: ``Path`` to the report to compare against - the before state.
+
+    Returns:
+        The ``CoverageDiff`` between the two coverage reports.
     """
 
     report = read_coverage_report(report)
@@ -928,9 +935,9 @@ def compute(
 
 @app.command()
 def compare(
-    report: Path = typer.Argument(..., help="Path to coverage report."),
+    report: Path = typer.Argument(..., help="Path to coverage report - the after state."),
     compare_report: Path = typer.Argument(
-        ..., help="Path to another coverage report to " "compare with."
+        ..., help="Path to another coverage report to compare with - the before state."
     ),
 ):
     """Compare two coverage reports generated by the compute command."""

tests/integration/patches/test_compare_new_column.patch

@@ -0,0 +1,14 @@
+Index: models/customers.sql
+===================================================================
+diff --git a/models/customers.sql b/models/customers.sql
+--- a/models/customers.sql	(revision b0b77aac70f490770a1e77c02bb0a2b8771d3203)
++++ b/models/customers.sql	(date 1745501614879)
+@@ -54,7 +54,8 @@
+         customer_orders.first_order,
+         customer_orders.most_recent_order,
+         customer_orders.number_of_orders,
+-        customer_payments.total_amount as customer_lifetime_value
++        customer_payments.total_amount as customer_lifetime_value,
++        1 as new_column
+
+     from customers

tests/integration/patches/test_compare_new_table.patch

@@ -0,0 +1,11 @@
+Index: models/new_table.sql
+===================================================================
+diff --git a/models/new_table.sql b/models/new_table.sql
+new file mode 100644
+--- /dev/null	(date 1745560791608)
++++ b/models/new_table.sql	(date 1745560791608)
+@@ -0,0 +1,4 @@
++select
++    1 as col_1,
++    2 as col_2,
++    3 as col_3

tests/integration/test_init.py

@@ -1,22 +1,43 @@
 import os
 import subprocess
 from pathlib import Path
+from tempfile import NamedTemporaryFile
 
 import psycopg2
 import pytest
 from psycopg2.extensions import ISOLATION_LEVEL_AUTOCOMMIT
 
-from dbt_coverage import CoverageType, do_compute
+from dbt_coverage import CoverageType, do_compare, do_compute
 
-DBT_PROJECT_PATH = "tests/integration/jaffle_shop"
+DBT_PROJECT_DIR = Path("tests/integration/jaffle_shop")
+PATCHES_DIR = Path("tests/integration/patches")
 DBT_ARGS = [
     "--profiles-dir",
     "tests/integration/profiles",
     "--project-dir",
-    DBT_PROJECT_PATH,
+    DBT_PROJECT_DIR,
 ]
 
 
+def apply_patch(patch_file: Path):
+    class ApplyPatch:
+        def __init__(self, patch_file: Path):
+            # We get the absolute path since the patch is run with a changed cwd
+            self.patch_file = patch_file.absolute()
+
+        def __enter__(self):
+            subprocess.run(
+                ["patch", "-p1", f"-i{self.patch_file}"], cwd=DBT_PROJECT_DIR, check=True
+            )
+
+        def __exit__(self, exc_type, exc_val, exc_tb):
+            subprocess.run(
+                ["patch", "-R", "-p1", f"-i{self.patch_file}"], cwd=DBT_PROJECT_DIR, check=True
+            )
+
+    return ApplyPatch(patch_file)
+
+
 @pytest.fixture(scope="session")
 def docker_compose_command():
     return "docker compose"
@@ -60,6 +81,27 @@ def session_setup_dbt(setup_postgres):
     This is a session fixture that can be used to accelerate tests if no tests change the models.
     """
 
+    run_dbt()
+
+
+@pytest.fixture()
+def setup_dbt(session_setup_dbt):
+    """Runs dbt and dbt docs generate before and after the test.
+
+    Use with tests that temporarily change the models.
+    """
+
+    # Setting up dbt before running the test is only necessary if it is the first test to run,
+    # or else it will all be already setup by the previous test.
+    # We replace the dbt setup before running the test by including session_setup_dbt fixture,
+    # which covers the case in which this tests runs first.
+
+    yield
+
+    run_dbt()
+
+
+def run_dbt():
     # Workaround for a bug - https://github.com/dbt-labs/dbt-core/issues/9138
     env = {**os.environ, "DBT_CLEAN_PROJECT_FILES_ONLY": "false"}
     subprocess.run(["dbt", "clean", *DBT_ARGS], env=env, check=True)
@@ -70,22 +112,22 @@ def session_setup_dbt(setup_postgres):
 
 
 def test_compute_doc(session_setup_dbt):
-    report = do_compute(Path(DBT_PROJECT_PATH), cov_type=CoverageType.DOC)
+    report = do_compute(DBT_PROJECT_DIR, cov_type=CoverageType.DOC)
 
     assert len(report.covered) == 15
     assert len(report.total) == 38
 
 
 def test_compute_test(session_setup_dbt):
-    report = do_compute(Path(DBT_PROJECT_PATH), cov_type=CoverageType.TEST)
+    report = do_compute(DBT_PROJECT_DIR, cov_type=CoverageType.TEST)
 
     assert len(report.covered) == 14
     assert len(report.total) == 38
 
 
 def test_compute_path_filter(session_setup_dbt):
     report = do_compute(
-        Path(DBT_PROJECT_PATH),
+        DBT_PROJECT_DIR,
         cov_type=CoverageType.DOC,
         model_path_filter=["models/staging"],
     )
@@ -98,7 +140,7 @@ def test_compute_path_filter(session_setup_dbt):
 
 def test_compute_path_exclusion_filter(session_setup_dbt):
     report = do_compute(
-        Path(DBT_PROJECT_PATH),
+        DBT_PROJECT_DIR,
         cov_type=CoverageType.DOC,
         model_path_exclusion_filter=["models/staging"],
     )
@@ -111,7 +153,7 @@ def test_compute_path_exclusion_filter(session_setup_dbt):
 
 def test_compute_both_path_filters(session_setup_dbt):
     report = do_compute(
-        Path(DBT_PROJECT_PATH),
+        DBT_PROJECT_DIR,
         cov_type=CoverageType.DOC,
         model_path_filter=["models/staging"],
         model_path_exclusion_filter=["models/staging/stg_customers"],
@@ -122,3 +164,45 @@ def test_compute_both_path_filters(session_setup_dbt):
     assert "jaffle_shop.stg_customers" not in report.subentities
     assert len(report.covered) == 0
     assert len(report.total) == 8
+
+
+def test_compare_no_change(session_setup_dbt):
+    with NamedTemporaryFile() as f1, NamedTemporaryFile() as f2:
+        do_compute(DBT_PROJECT_DIR, cov_type=CoverageType.DOC, cov_report=Path(f1.name))
+        do_compute(DBT_PROJECT_DIR, cov_type=CoverageType.DOC, cov_report=Path(f2.name))
+
+        diff = do_compare(Path(f2.name), Path(f1.name))
+
+    assert len(diff.new_misses) == 0
+
+
+def test_compare_new_column(setup_dbt):
+    with NamedTemporaryFile() as f1, NamedTemporaryFile() as f2:
+        do_compute(DBT_PROJECT_DIR, cov_type=CoverageType.DOC, cov_report=Path(f1.name))
+        with apply_patch(PATCHES_DIR / "test_compare_new_column.patch"):
+            run_dbt()
+            do_compute(DBT_PROJECT_DIR, cov_type=CoverageType.DOC, cov_report=Path(f2.name))
+
+        diff = do_compare(Path(f2.name), Path(f1.name))
+
+    newly_missed_tables = diff.new_misses
+    assert set(newly_missed_tables) == {"jaffle_shop.customers"}
+    newly_missed_table = list(newly_missed_tables.values())[0]
+    newly_missed_columns = set(newly_missed_table.new_misses.keys())
+    assert newly_missed_columns == {"new_column"}
+
+
+def test_compare_new_table(setup_dbt):
+    with NamedTemporaryFile() as f1, NamedTemporaryFile() as f2:
+        do_compute(DBT_PROJECT_DIR, cov_type=CoverageType.DOC, cov_report=Path(f1.name))
+        with apply_patch(PATCHES_DIR / "test_compare_new_table.patch"):
+            run_dbt()
+            do_compute(DBT_PROJECT_DIR, cov_type=CoverageType.DOC, cov_report=Path(f2.name))
+
+        diff = do_compare(Path(f2.name), Path(f1.name))
+
+    newly_missed_tables = diff.new_misses
+    assert set(newly_missed_tables) == {"jaffle_shop.new_table"}
+    newly_missed_table = list(newly_missed_tables.values())[0]
+    newly_missed_columns = set(newly_missed_table.new_misses.keys())
+    assert newly_missed_columns == {"col_1", "col_2", "col_3"}