test: snapshot tests for diagrams (#239)

Closes #175.

### Summary of Changes
Created tests to check if there are any graphic changes in the seaborn
library by adding legacy graphics to compare to

Co-authored-by: patrikguempel
<128832338+patrikguempel@users.noreply.github.com>

---------

Co-authored-by: megalinter-bot <129584137+megalinter-bot@users.noreply.github.com>
Co-authored-by: Lars Reimann <mail@larsreimann.com>

tests/safeds/data/tabular/containers/_column/test_plot_boxplot.py

@@ -1,29 +1,20 @@
-import _pytest
-import matplotlib.pyplot as plt
 import pytest
+from safeds.data.image.containers import Image
 from safeds.data.tabular.containers import Table
 from safeds.data.tabular.exceptions import NonNumericColumnError
 
+from tests.helpers import resolve_resource_path
 
-def test_plot_boxplot_complex() -> None:
-    with pytest.raises(NotImplementedError):  # noqa: PT012
-        table = Table.from_dict({"A": [1, 2, complex(1, -2)]})
-        table.get_column("A").plot_boxplot()
+
+def test_should_match_snapshot() -> None:
+    table = Table.from_dict({"A": [1, 2, 3]})
+    table.get_column("A").plot_boxplot()
+    current = table.get_column("A").plot_boxplot()
+    snapshot = Image.from_png_file(resolve_resource_path("./image/snapshot_boxplot.png"))
+    assert snapshot._image.tobytes() == current._image.tobytes()
 
 
-def test_plot_boxplot_non_numeric() -> None:
+def test_should_raise_if_column_contains_non_numerical_values() -> None:
     table = Table.from_dict({"A": [1, 2, "A"]})
     with pytest.raises(NonNumericColumnError):
         table.get_column("A").plot_boxplot()
-
-
-def test_plot_boxplot_float(monkeypatch: _pytest.monkeypatch) -> None:
-    monkeypatch.setattr(plt, "show", lambda: None)
-    table = Table.from_dict({"A": [1, 2, 3.5]})
-    table.get_column("A").plot_boxplot()
-
-
-def test_plot_boxplot_int(monkeypatch: _pytest.monkeypatch) -> None:
-    monkeypatch.setattr(plt, "show", lambda: None)
-    table = Table.from_dict({"A": [1, 2, 3]})
-    table.get_column("A").plot_boxplot()

tests/safeds/data/tabular/containers/_column/test_plot_histogram.py

@@ -1,9 +1,18 @@
-import _pytest
-import matplotlib.pyplot as plt
+from safeds.data.image.containers import Image
 from safeds.data.tabular.containers import Table
 
+from tests.helpers import resolve_resource_path
 
-def test_plot_histogram(monkeypatch: _pytest.monkeypatch) -> None:
-    monkeypatch.setattr(plt, "show", lambda: None)
+
+def test_should_match_snapshot_numeric() -> None:
     table = Table.from_dict({"A": [1, 2, 3]})
-    table.get_column("A").plot_histogram()
+    current = table.get_column("A").plot_histogram()
+    snapshot = Image.from_png_file(resolve_resource_path("./image/snapshot_histogram_numeric.png"))
+    assert snapshot._image.tobytes() == current._image.tobytes()
+
+
+def test_should_match_snapshot_str() -> None:
+    table = Table.from_dict({"A": ["A", "B", "Apple"]})
+    current = table.get_column("A").plot_histogram()
+    snapshot = Image.from_png_file(resolve_resource_path("./image/snapshot_histogram_str.png"))
+    assert snapshot._image.tobytes() == current._image.tobytes()

tests/safeds/data/tabular/containers/_table/test_plot_correlation_heatmap.py

@@ -1,15 +1,11 @@
-import _pytest
-import matplotlib.pyplot as plt
+from safeds.data.image.containers import Image
 from safeds.data.tabular.containers import Table
 
+from tests.helpers import resolve_resource_path
 
-def test_plot_correlation_heatmap_non_numeric(monkeypatch: _pytest.monkeypatch) -> None:
-    monkeypatch.setattr(plt, "show", lambda: None)
-    table = Table.from_dict({"A": [1, 2, "A"], "B": [1, 2, 3]})
-    table.plot_correlation_heatmap()
 
-
-def test_plot_correlation_heatmap(monkeypatch: _pytest.monkeypatch) -> None:
-    monkeypatch.setattr(plt, "show", lambda: None)
-    table = Table.from_dict({"A": [1, 2, 3.5], "B": [2, 4, 7]})
-    table.plot_correlation_heatmap()
+def test_should_match_snapshot() -> None:
+    table = Table.from_dict({"A": [1, 2, 3.5], "B": [0.2, 4, 77]})
+    current = table.plot_correlation_heatmap()
+    legacy = Image.from_png_file(resolve_resource_path("./image/snapshot_heatmap.png"))
+    assert legacy._image.tobytes() == current._image.tobytes()

tests/safeds/data/tabular/containers/_table/test_plot_lineplot.py

@@ -1,17 +1,19 @@
-import _pytest
-import matplotlib.pyplot as plt
 import pytest
+from safeds.data.image.containers import Image
 from safeds.data.tabular.containers import Table
 from safeds.data.tabular.exceptions import UnknownColumnNameError
 
+from tests.helpers import resolve_resource_path
 
-def test_plot_lineplot(monkeypatch: _pytest.monkeypatch) -> None:
-    monkeypatch.setattr(plt, "show", lambda: None)
+
+def test_should_match_snapshot() -> None:
     table = Table.from_dict({"A": [1, 2, 3], "B": [2, 4, 7]})
-    table.plot_lineplot("A", "B")
+    current = table.plot_lineplot("A", "B")
+    snapshot = Image.from_png_file(resolve_resource_path("./image/snapshot_lineplot.png"))
+    assert snapshot._image.tobytes() == current._image.tobytes()
 
 
-def test_plot_lineplot_wrong_column_name() -> None:
+def test_should_raise_if_column_does_not_exist() -> None:
     table = Table.from_dict({"A": [1, 2, 3], "B": [2, 4, 7]})
     with pytest.raises(UnknownColumnNameError):
         table.plot_lineplot("C", "A")

tests/safeds/data/tabular/containers/_table/test_plot_scatterplot.py

@@ -1,17 +1,19 @@
-import _pytest
-import matplotlib.pyplot as plt
 import pytest
+from safeds.data.image.containers import Image
 from safeds.data.tabular.containers import Table
 from safeds.data.tabular.exceptions import UnknownColumnNameError
 
+from tests.helpers import resolve_resource_path
 
-def test_plot_scatterplot(monkeypatch: _pytest.monkeypatch) -> None:
-    monkeypatch.setattr(plt, "show", lambda: None)
+
+def test_should_match_snapshot() -> None:
     table = Table.from_dict({"A": [1, 2, 3], "B": [2, 4, 7]})
-    table.plot_scatterplot("A", "B")
+    current = table.plot_scatterplot("A", "B")
+    snapshot = Image.from_png_file(resolve_resource_path("./image/snapshot_scatterplot.png"))
+    assert snapshot._image.tobytes() == current._image.tobytes()
 
 
-def test_plot_scatterplot_wrong_column_name() -> None:
+def test_should_raise_if_column_does_not_exist() -> None:
     table = Table.from_dict({"A": [1, 2, 3], "B": [2, 4, 7]})
     with pytest.raises(UnknownColumnNameError):
         table.plot_scatterplot("C", "A")