Improve validation error messages (#56)

changelog.d/20250212_155835_michalportes1_error_messages.md

@@ -0,0 +1,40 @@
+<!--
+A new scriv changelog fragment.
+
+Uncomment the section that is right (remove the HTML comment wrapper).
+-->
+
+<!--
+### Removed
+
+- A bullet item for the Removed category.
+
+-->
+<!--
+### Added
+
+- A bullet item for the Added category.
+
+-->
+### Changed
+
+- More descriptive validation error messages
+
+<!--
+### Deprecated
+
+- A bullet item for the Deprecated category.
+
+-->
+<!--
+### Fixed
+
+- A bullet item for the Fixed category.
+
+-->
+<!--
+### Security
+
+- A bullet item for the Security category.
+
+-->

src/pictureshow/core.py

@@ -146,7 +146,9 @@ def _validate_page_size(page_size, landscape):
                     f' please use one of: {", ".join(PAGE_SIZES)}'
                 ) from err
 
-        page_size_error = PageSizeError('two positive numbers expected')
+        page_size_error = PageSizeError(
+            f'expected two positive numbers, got {page_size!r}'
+        )
         try:
             page_width, page_height = page_size
             if page_width <= 0 or page_height <= 0:
@@ -170,7 +172,7 @@ def _validate_color(color):
 
     @staticmethod
     def _validate_layout(layout):
-        layout_error = LayoutError('two positive integers expected')
+        layout_error = LayoutError(f'expected two positive integers, got {layout!r}')
         try:
             if isinstance(layout, str):
                 layout = tuple(int(s) for s in DELIMITER.split(layout))

tests/test_cli.py

@@ -144,22 +144,26 @@ def test_multiple_pictures_layout(self, capsys, new_pdf, layout, num_pages, page
         assert f'Saved 6 pictures ({pages}) to ' in std_out
         assert_pdf(new_pdf, num_pages=num_pages)
 
-    @pytest.mark.parametrize(
-        'layout',
-        (
-            pytest.param('1', id='invalid format'),
-            pytest.param('0x1', id='invalid value'),
-        ),
-    )
-    def test_invalid_layout_throws_error(self, capsys, new_pdf, layout):
-        argv = f'{PIC_FILE} -o {new_pdf} -l {layout}'.split()
+    def test_invalid_layout_format_raises_error(self, capsys, new_pdf):
+        argv = f'{PIC_FILE} -o {new_pdf} -l 1'.split()
+        with pytest.raises(SystemExit) as exc:
+            main(argv)
+        exit_code = exc.value.args[0]
+        std_err = capsys.readouterr().err
+
+        assert exit_code == 2
+        assert "LayoutError: expected two positive integers, got '1'" in std_err
+        assert not new_pdf.exists()
+
+    def test_invalid_layout_value_raises_error(self, capsys, new_pdf):
+        argv = f'{PIC_FILE} -o {new_pdf} -l 0x1'.split()
         with pytest.raises(SystemExit) as exc:
             main(argv)
         exit_code = exc.value.args[0]
         std_err = capsys.readouterr().err
 
         assert exit_code == 2
-        assert 'LayoutError: two positive integers expected' in std_err
+        assert "LayoutError: expected two positive integers, got '0x1'" in std_err
         assert not new_pdf.exists()
 
     def test_existing_target_file_throws_error(self, capsys, existing_pdf):

tests/test_pictures_to_pdf.py

@@ -146,7 +146,9 @@ def test_layout(new_pdf):
 
 
 def test_invalid_layout_raises_error(new_pdf):
-    with pytest.raises(LayoutError, match='two positive integers expected'):
+    with pytest.raises(
+            LayoutError, match=r'expected two positive integers, got \(1, 0\)'
+    ):
         pictures_to_pdf(PIC_FILE, output_file=new_pdf, layout=(1, 0))
 
     assert not new_pdf.exists()

tests/unit_test.py

@@ -230,7 +230,9 @@ def test_landscape_unchanged(self, page_size, expected):
         ),
     )
     def test_invalid_page_size_raises_error(self, page_size):
-        with pytest.raises(PageSizeError, match='two positive numbers expected'):
+        with pytest.raises(
+                PageSizeError, match=r'expected two positive numbers, got \(.+\)'
+        ):
             PictureShow()._validate_page_size(page_size, landscape=False)
 
     def test_invalid_page_size_name_raises_error(self):
@@ -302,8 +304,10 @@ def test_str(self, layout, expected):
             pytest.param((1, 1.0), id='invalid type'),
         ),
     )
-    def test_invalid_layout_raises_error(self, layout):
-        with pytest.raises(LayoutError, match='two positive integers expected'):
+    def test_invalid_layout_tuple_raises_error(self, layout):
+        with pytest.raises(
+                LayoutError, match=r'expected two positive integers, got \(.+\)'
+        ):
             PictureShow()._validate_layout(layout)
 
     @pytest.mark.parametrize(
@@ -314,7 +318,9 @@ def test_invalid_layout_raises_error(self, layout):
         ),
     )
     def test_invalid_layout_str_raises_error(self, layout):
-        with pytest.raises(LayoutError, match='two positive integers expected'):
+        with pytest.raises(
+                LayoutError, match="expected two positive integers, got '.+'"
+        ):
             PictureShow()._validate_layout(layout)