1 files changed, 178 insertions, 0 deletions
diff --git a/tests/test_markdown_lexer.py b/tests/test_markdown_lexer.py
new file mode 100644
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+++ b/tests/test_markdown_lexer.py
@@ -0,0 +1,178 @@
+"""
+    Pygments Markdown lexer tests
+    ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+    :copyright: Copyright 2006-2022 by the Pygments team, see AUTHORS.
+    :license: BSD, see LICENSE for details.
+"""
+
+import pytest
+from pygments.token import Generic, Token, String
+
+from pygments.lexers.markup import MarkdownLexer
+
+
+@pytest.fixture(scope='module')
+def lexer():
+    yield MarkdownLexer()
+
+
+def assert_same_text(lexer, text):
+    """Show that lexed markdown does not remove any content. """
+    tokens = list(lexer.get_tokens_unprocessed(text))
+    output = ''.join(t[2] for t in tokens)
+    assert text == output
+
+
+def test_code_fence(lexer):
+    assert_same_text(lexer, r'```\nfoo\n```\n')
+
+
+def test_code_fence_gsm(lexer):
+    assert_same_text(lexer, r'```markdown\nfoo\n```\n')
+
+
+def test_code_fence_gsm_with_no_lexer(lexer):
+    assert_same_text(lexer, r'```invalid-lexer\nfoo\n```\n')
+
+
+def test_invalid_atx_heading(lexer):
+    fragments = (
+        '#',
+        'a #',
+        '*#',
+    )
+
+    for fragment in fragments:
+        for token, _ in lexer.get_tokens(fragment):
+            assert token != Generic.Heading
+
+
+def test_atx_heading(lexer):
+    fragments = (
+        '#Heading',
+        '# Heading',
+        '# Another heading',
+        '# Another # heading',
+        '# Heading #',
+    )
+
+    for fragment in fragments:
+        tokens = [
+            (Generic.Heading, fragment),
+            (Token.Text, '\n'),
+        ]
+        assert list(lexer.get_tokens(fragment)) == tokens
+
+
+def test_invalid_atx_subheading(lexer):
+    fragments = (
+        '##',
+        'a ##',
+        '*##',
+        '####### too many hashes'
+    )
+
+    for fragment in fragments:
+        for token, _ in lexer.get_tokens(fragment):
+            assert token != Generic.Subheading
+
+
+def test_atx_subheading(lexer):
+    fragments = (
+        '##Subheading',
+        '## Subheading',
+        '### Subheading',
+        '#### Subheading',
+        '##### Subheading',
+        '###### Subheading',
+        '## Another subheading',
+        '## Another ## subheading',
+        '###### Subheading #',
+        '###### Subheading ######',
+    )
+
+    for fragment in fragments:
+        tokens = [
+            (Generic.Subheading, fragment),
+            (Token.Text, '\n'),
+        ]
+        assert list(lexer.get_tokens(fragment)) == tokens
+
+
+def test_invalid_setext_heading(lexer):
+    fragments = (
+        'Heading\n',
+        'Heading\n_',
+        'Heading\n =====',
+        'Heading\na=====',
+        '=====',
+        '\n=\n',
+        'Heading\n=====Text'
+    )
+
+    for fragment in fragments:
+        for token, _ in lexer.get_tokens(fragment):
+            assert token != Generic.Heading
+
+
+def test_setext_heading(lexer):
+    fragments = (
+        'Heading\n=',
+        'Heading\n=======',
+        'Heading\n==========',
+    )
+
+    for fragment in fragments:
+        tokens = [
+            (Generic.Heading, fragment.split('\n')[0]),
+            (Token.Text, '\n'),
+            (Generic.Heading, fragment.split('\n')[1]),
+            (Token.Text, '\n'),
+        ]
+        assert list(lexer.get_tokens(fragment)) == tokens
+
+
+def test_invalid_setext_subheading(lexer):
+    fragments = (
+        'Subheading\n',
+        'Subheading\n_',
+        'Subheading\n -----',
+        'Subheading\na-----',
+        '-----',
+        '\n-\n',
+        'Subheading\n-----Text'
+    )
+
+    for fragment in fragments:
+        for token, _ in lexer.get_tokens(fragment):
+            assert token != Generic.Subheading
+
+
+def test_setext_subheading(lexer):
+    fragments = (
+        'Subheading\n-',
+        'Subheading\n----------',
+        'Subheading\n-----------',
+    )
+
+    for fragment in fragments:
+        tokens = [
+            (Generic.Subheading, fragment.split('\n')[0]),
+            (Token.Text, '\n'),
+            (Generic.Subheading, fragment.split('\n')[1]),
+            (Token.Text, '\n'),
+        ]
+        assert list(lexer.get_tokens(fragment)) == tokens
+
+
+def test_invalid_code_block(lexer):
+    fragments = (
+        '```code```',
+        'prefix not allowed before ```\ncode block\n```'
+        '   code',
+    )
+
+    for fragment in fragments:
+        for token, _ in lexer.get_tokens(fragment):
+            assert token != String.Backtick