test(core): add tests for Recipe and Step repr

tests/test_pprint.py

@@ -0,0 +1,52 @@
+import pytest
+
+import ibis_ml as ml
+
+
+@pytest.fixture()
+def rec():
+    imputer = ml.ImputeMean(ml.numeric())
+    scaler = ml.ScaleStandard(ml.numeric())
+    encoder = ml.OneHotEncode(ml.string(), min_frequency=20, max_categories=10)
+    return ml.Recipe(imputer, scaler, encoder)
+
+
+@pytest.fixture()
+def pipe(rec):
+    pytest.importorskip("sklearn")
+    from sklearn.pipeline import Pipeline
+    from sklearn.svm import SVC
+
+    return Pipeline([("rec", rec), ("svc", SVC())])
+
+
+def test_steps(rec):
+    expected = [
+        "ImputeMean(numeric())",
+        "ScaleStandard(numeric())",
+        "OneHotEncode(string(), min_frequency=20, max_categories=10)",
+    ]
+    assert [repr(step) for step in rec.steps] == expected
+
+
+def test_recipe(rec):
+    expected = """
+Recipe(ImputeMean(numeric()),
+       ScaleStandard(numeric()),
+       OneHotEncode(string(), min_frequency=20, max_categories=10))"""
+
+    expected = expected[1:]  # remove first \n
+    assert repr(rec) == expected
+
+
+def test_recipe_in_sklearn_pipeline(pipe):
+    expected = """
+Pipeline(steps=[('rec',
+                 Recipe(ImputeMean(numeric()), ScaleStandard(numeric()),
+                        OneHotEncode(string(),
+                                     min_frequency=20,
+                                     max_categories=10))),
+                ('svc', SVC())])"""
+
+    expected = expected[1:]  # remove first \n
+    assert repr(pipe) == expected