Update th/td to use style attribute

This allows better interoperation with CSS style sheets, as the align
object on the TH is skipped if the css uses 'text-align: inherit' and
the previous 'text-align' is used instead (or the default: left).

Added an override to restore the original `align` behavior
Moved existing tests to the new test infrastructure
Added new tests to test the configuration parameter
Updated documentation to document the configuration parameter.

8 files changed, 943 insertions, 641 deletions

diff --git a/docs/change_log/index.md b/docs/change_log/index.md
index 09ace62..fc78087 100644
--- a/docs/change_log/index.md
+++ b/docs/change_log/index.md
@@ -3,6 +3,8 @@ title: Change Log
 Python-Markdown Change Log
 =========================
 
+Under development: version 3.4.0 ([Notes](release-3.4.md)).
+
 May 5, 2022: version 3.3.7 (a bug-fix release).
 
 * Disallow square brackets in reference link ids (#1209).
diff --git a/docs/change_log/release-3.4.md b/docs/change_log/release-3.4.md
new file mode 100644
index 0000000..0070da9
--- /dev/null
+++ b/docs/change_log/release-3.4.md
@@ -0,0 +1,44 @@
+title: Release Notes for v3.4
+
+# Python-Markdown 3.4 Release Notes
+
+Python-Markdown version 3.4 supports Python versions 3.6, 3.7, 3.8, 3.9 and PyPy3.
+
+## Backwards-incompatible changes
+
+### The `table` extension now uses a `style` attribute instead of `align` attribute for alignment.
+
+The [HTML4 spec][spec4] specifically
+deprecates the use of the `align` attribute and it does not appear at all in the 
+[HTML5 spec][spec5]. Therefore, by default, the [table] extension will now use the `style`
+attribute (setting just the `text-align` property) in `td` and `th` blocks.
+
+[spec4]: https://www.w3.org/TR/html4/present/graphics.html#h-15.1.2
+[spec5]: https://www.w3.org/TR/html53/tabular-data.html#attributes-common-to-td-and-th-elements
+
+The former behavior is available by setting the setting `use_align_attribute` configuration
+option to `True` when adding the extension.
+
+For example, to configure the old `align` behavior:
+
+```python
+from markdown.extensions.tables import TableExtension
+
+markdown.markdown(src, extensions=[TableExtension(use_align_attribute=True)])
+```
+
+In addition, tests were moved to the modern test environment.
+
+## New features
+
+The following new features have been included in the 3.3 release:
+
+* Use `style` attribute in tables for alignment instead of `align` for better CSS
+  inter-operation. The old behavior is available by setting `use_align_attribute=True` when
+  adding the extension.
+
+## Bug fixes
+
+The following bug fixes are included in the 3.4 release:
+
+
diff --git a/docs/extensions/tables.md b/docs/extensions/tables.md
index 30b7636..aaffc09 100644
--- a/docs/extensions/tables.md
+++ b/docs/extensions/tables.md
@@ -58,10 +58,30 @@ Usage
 See [Extensions](index.md) for general extension usage. Use `tables` as the
 name of the extension.
 
-This extension does not accept any special configuration options.
+See the [Library Reference](../reference.md#extensions) for information about
+configuring extensions.
+
+The following options are provided to change the default behavior:
+
+* **`use_align_attribute`**: Set to `True` to use `align` instead of an appropriate `style` attribute
+
+    Default: `'False'`
+
 
 A trivial example:
 
 ```python
 markdown.markdown(some_text, extensions=['tables'])
 ```
+
+### Examples
+
+For an example, let us suppose that alignment should be controlled by the legacy `align`
+attribute.
+
+```pycon
+>>> from markdown.extensions.tables import TableExtension
+>>> html = markdown.markdown(text,
+...                 extensions=[TableExtension(use_align_attribute=True)]
+... )
+```
diff --git a/markdown/extensions/tables.py b/markdown/extensions/tables.py
index 0a9d084..c8b1024 100644
--- a/markdown/extensions/tables.py
+++ b/markdown/extensions/tables.py
@@ -30,9 +30,11 @@ class TableProcessor(BlockProcessor):
     RE_CODE_PIPES = re.compile(r'(?:(\\\\)|(\\`+)|(`+)|(\\\|)|(\|))')
     RE_END_BORDER = re.compile(r'(?<!\\)(?:\\\\)*\|$')
 
-    def __init__(self, parser):
+    def __init__(self, parser, config):
         self.border = False
         self.separator = ''
+        self.config = config
+
         super().__init__(parser)
 
     def test(self, parent, block):
@@ -126,7 +128,10 @@ class TableProcessor(BlockProcessor):
             except IndexError:  # pragma: no cover
                 c.text = ""
             if a:
-                c.set('align', a)
+                if self.config['use_align_attribute']:
+                    c.set('align', a)
+                else:
+                    c.set('style', f'text-align: {a};')
 
     def _split_row(self, row):
         """ split a row of text into list of cells. """
@@ -212,11 +217,19 @@ class TableProcessor(BlockProcessor):
 class TableExtension(Extension):
     """ Add tables to Markdown. """
 
+    def __init__(self, **kwargs):
+        self.config = {
+            'use_align_attribute': [False, 'True to use align attribute instead of style.'],
+        }
+
+        super().__init__(**kwargs)
+
     def extendMarkdown(self, md):
         """ Add an instance of TableProcessor to BlockParser. """
         if '|' not in md.ESCAPED_CHARS:
             md.ESCAPED_CHARS.append('|')
-        md.parser.blockprocessors.register(TableProcessor(md.parser), 'table', 75)
+        processor = TableProcessor(md.parser, self.getConfigs())
+        md.parser.blockprocessors.register(processor, 'table', 75)
 
 
 def makeExtension(**kwargs):  # pragma: no cover
diff --git a/tests/extensions/extra/tables.html b/tests/extensions/extra/tables.html
deleted file mode 100644
index 25dee48..0000000
--- a/tests/extensions/extra/tables.html
+++ /dev/null
@@ -1,466 +0,0 @@
-<h2>Table Tests</h2>
-<table>
-<thead>
-<tr>
-<th>First Header</th>
-<th>Second Header</th>
-</tr>
-</thead>
-<tbody>
-<tr>
-<td>Content Cell</td>
-<td>Content Cell</td>
-</tr>
-<tr>
-<td>Content Cell</td>
-<td>Content Cell</td>
-</tr>
-</tbody>
-</table>
-<table>
-<thead>
-<tr>
-<th>First Header</th>
-<th>Second Header</th>
-</tr>
-</thead>
-<tbody>
-<tr>
-<td>Content Cell</td>
-<td>Content Cell</td>
-</tr>
-<tr>
-<td>Content Cell</td>
-<td>Content Cell</td>
-</tr>
-</tbody>
-</table>
-<table>
-<thead>
-<tr>
-<th align="left">Item</th>
-<th align="right">Value</th>
-</tr>
-</thead>
-<tbody>
-<tr>
-<td align="left">Computer</td>
-<td align="right">$1600</td>
-</tr>
-<tr>
-<td align="left">Phone</td>
-<td align="right">$12</td>
-</tr>
-<tr>
-<td align="left">Pipe</td>
-<td align="right">$1</td>
-</tr>
-</tbody>
-</table>
-<table>
-<thead>
-<tr>
-<th>Function name</th>
-<th>Description</th>
-</tr>
-</thead>
-<tbody>
-<tr>
-<td><code>help()</code></td>
-<td>Display the help window.</td>
-</tr>
-<tr>
-<td><code>destroy()</code></td>
-<td><strong>Destroy your computer!</strong></td>
-</tr>
-</tbody>
-</table>
-<table>
-<thead>
-<tr>
-<th align="left">foo</th>
-<th align="center">bar</th>
-<th align="right">baz</th>
-</tr>
-</thead>
-<tbody>
-<tr>
-<td align="left"></td>
-<td align="center">Q</td>
-<td align="right"></td>
-</tr>
-<tr>
-<td align="left">W</td>
-<td align="center"></td>
-<td align="right">W</td>
-</tr>
-</tbody>
-</table>
-<table>
-<thead>
-<tr>
-<th>foo</th>
-<th>bar</th>
-<th>baz</th>
-</tr>
-</thead>
-<tbody>
-<tr>
-<td></td>
-<td>Q</td>
-<td></td>
-</tr>
-<tr>
-<td>W</td>
-<td></td>
-<td>W</td>
-</tr>
-</tbody>
-</table>
-<p>Three spaces in front of a table:</p>
-<table>
-<thead>
-<tr>
-<th>First Header</th>
-<th>Second Header</th>
-</tr>
-</thead>
-<tbody>
-<tr>
-<td>Content Cell</td>
-<td>Content Cell</td>
-</tr>
-<tr>
-<td>Content Cell</td>
-<td>Content Cell</td>
-</tr>
-</tbody>
-</table>
-<table>
-<thead>
-<tr>
-<th>First Header</th>
-<th>Second Header</th>
-</tr>
-</thead>
-<tbody>
-<tr>
-<td>Content Cell</td>
-<td>Content Cell</td>
-</tr>
-<tr>
-<td>Content Cell</td>
-<td>Content Cell</td>
-</tr>
-</tbody>
-</table>
-<p>Four spaces is a code block:</p>
-<pre><code>First Header | Second Header
------------- | -------------
-Content Cell | Content Cell
-Content Cell | Content Cell
-</code></pre>
-<table>
-<thead>
-<tr>
-<th>First Header</th>
-<th>Second Header</th>
-</tr>
-</thead>
-<tbody>
-<tr>
-<td></td>
-<td></td>
-</tr>
-</tbody>
-</table>
-<p>More inline code block tests</p>
-<table>
-<thead>
-<tr>
-<th>Column 1</th>
-<th>Column 2</th>
-<th>Column 3</th>
-</tr>
-</thead>
-<tbody>
-<tr>
-<td>word 1</td>
-<td>word 2</td>
-<td>word 3</td>
-</tr>
-<tr>
-<td>word 1</td>
-<td><code>word 2</code></td>
-<td>word 3</td>
-</tr>
-<tr>
-<td>word 1</td>
-<td>`word 2</td>
-<td>word 3</td>
-</tr>
-<tr>
-<td>word 1</td>
-<td>`word 2</td>
-<td>word 3</td>
-</tr>
-<tr>
-<td>word 1</td>
-<td><code>word |2</code></td>
-<td>word 3</td>
-</tr>
-<tr>
-<td>words</td>
-<td><code>some | code</code></td>
-<td>more words</td>
-</tr>
-<tr>
-<td>words</td>
-<td><code>some | code</code></td>
-<td>more words</td>
-</tr>
-<tr>
-<td>words</td>
-<td><code>some | code</code></td>
-<td>more words</td>
-</tr>
-<tr>
-<td>words</td>
-<td><code>some ` | ` code</code></td>
-<td>more words</td>
-</tr>
-<tr>
-<td>words</td>
-<td><code>some ` | ` code</code></td>
-<td>more words</td>
-</tr>
-<tr>
-<td>words</td>
-<td><code>some ` | ` code</code></td>
-<td>more words</td>
-</tr>
-</tbody>
-</table>
-<p>A test for issue #440:</p>
-<table>
-<thead>
-<tr>
-<th>foo</th>
-<th>bar</th>
-</tr>
-</thead>
-<tbody>
-<tr>
-<td>foo</td>
-<td>(<code>bar</code>) and <code>baz</code>.</td>
-</tr>
-</tbody>
-</table>
-<p>Lists are not tables</p>
-<ul>
-<li>this | should | not</li>
-<li>be | a | table</li>
-</ul>
-<p>Add tests for issue #449</p>
-<table>
-<thead>
-<tr>
-<th>Odd backticks</th>
-<th>Even backticks</th>
-</tr>
-</thead>
-<tbody>
-<tr>
-<td><code>[!\"\#$%&amp;'()*+,\-./:;&lt;=&gt;?@\[\\\]^_`{|}~]</code></td>
-<td><code>[!\"\#$%&amp;'()*+,\-./:;&lt;=&gt;?@\[\\\]^`_`{|}~]</code></td>
-</tr>
-</tbody>
-</table>
-<table>
-<thead>
-<tr>
-<th>Escapes</th>
-<th>More Escapes</th>
-</tr>
-</thead>
-<tbody>
-<tr>
-<td><code>`\</code></td>
-<td><code>\</code></td>
-</tr>
-</tbody>
-</table>
-<p>Only the first backtick can be escaped</p>
-<table>
-<thead>
-<tr>
-<th>Escaped</th>
-<th>Bacticks</th>
-</tr>
-</thead>
-<tbody>
-<tr>
-<td>`<code>\</code></td>
-<td>``</td>
-</tr>
-</tbody>
-</table>
-<p>Test escaped pipes</p>
-<table>
-<thead>
-<tr>
-<th>Column 1</th>
-<th>Column 2</th>
-</tr>
-</thead>
-<tbody>
-<tr>
-<td><code>|</code> |</td>
-<td>Pipes are okay in code and escaped. |</td>
-</tr>
-</tbody>
-</table>
-<table>
-<thead>
-<tr>
-<th>Column 1</th>
-<th>Column 2</th>
-</tr>
-</thead>
-<tbody>
-<tr>
-<td>row1</td>
-<td>row1    |</td>
-</tr>
-<tr>
-<td>row2</td>
-<td>row2</td>
-</tr>
-</tbody>
-</table>
-<p>Test header escapes</p>
-<table>
-<thead>
-<tr>
-<th><code>`\</code> |</th>
-<th><code>\</code> |</th>
-</tr>
-</thead>
-<tbody>
-<tr>
-<td>row1</td>
-<td>row1</td>
-</tr>
-<tr>
-<td>row2</td>
-<td>row2</td>
-</tr>
-</tbody>
-</table>
-<p>Escaped pipes in format row should not be a table</p>
-<p>| Column1   | Column2 |
-| ------- || ------- |
-| row1      | row1    |
-| row2      | row2    |</p>
-<p>Test escaped code in Table</p>
-<table>
-<thead>
-<tr>
-<th>Should not be code</th>
-<th>Should be code</th>
-</tr>
-</thead>
-<tbody>
-<tr>
-<td>`Not code`</td>
-<td>\<code>code</code></td>
-</tr>
-<tr>
-<td>\`Not code\`</td>
-<td>\\<code>code</code></td>
-</tr>
-</tbody>
-</table>
-<p>Single column tables</p>
-<table>
-<thead>
-<tr>
-<th>Is a Table</th>
-</tr>
-</thead>
-<tbody>
-<tr>
-<td></td>
-</tr>
-</tbody>
-</table>
-<table>
-<thead>
-<tr>
-<th>Is a Table</th>
-</tr>
-</thead>
-<tbody>
-<tr>
-<td></td>
-</tr>
-</tbody>
-</table>
-<table>
-<thead>
-<tr>
-<th>Is a Table</th>
-</tr>
-</thead>
-<tbody>
-<tr>
-<td></td>
-</tr>
-</tbody>
-</table>
-<table>
-<thead>
-<tr>
-<th>Is a Table</th>
-</tr>
-</thead>
-<tbody>
-<tr>
-<td>row</td>
-</tr>
-</tbody>
-</table>
-<table>
-<thead>
-<tr>
-<th>Is a Table</th>
-</tr>
-</thead>
-<tbody>
-<tr>
-<td>row</td>
-</tr>
-</tbody>
-</table>
-<table>
-<thead>
-<tr>
-<th>Is a Table</th>
-</tr>
-</thead>
-<tbody>
-<tr>
-<td>row</td>
-</tr>
-</tbody>
-</table>
-<h2>| Is not a Table</h2>
-<p>| row</p>
-<h2>Is not a Table |</h2>
-<p>row            |</p>
-<p>| Is not a Table
-| --------------
-row</p>
-<p>Is not a Table |
--------------- |
-row</p>
\ No newline at end of file
diff --git a/tests/extensions/extra/tables.txt b/tests/extensions/extra/tables.txt
deleted file mode 100644
index 2dc4967..0000000
--- a/tests/extensions/extra/tables.txt
+++ /dev/null
@@ -1,169 +0,0 @@
-Table Tests
------------
-
-First Header  | Second Header
-------------- | -------------
-Content Cell  | Content Cell
-Content Cell  | Content Cell
-
-| First Header  | Second Header |
-| ------------- | ------------- |
-| Content Cell  | Content Cell  |
-| Content Cell  | Content Cell  |
-
-| Item      | Value |
-| :-------- | -----:|
-| Computer  | $1600 |
-| Phone     |   $12 |
-| Pipe      |    $1 |
-
-| Function name | Description                    |
-| ------------- | ------------------------------ |
-| `help()`      | Display the help window.       |
-| `destroy()`   | **Destroy your computer!**     |
-
-|foo|bar|baz|
-|:--|:-:|--:|
-|   | Q |   |
-|W  |   |  W|
-
-foo|bar|baz
----|---|---
-   | Q |
- W |   | W
-
-Three spaces in front of a table:
-
-   First Header | Second Header
-   ------------ | -------------
-   Content Cell | Content Cell
-   Content Cell | Content Cell
-
-   | First Header | Second Header |
-   | ------------ | ------------- |
-   | Content Cell | Content Cell  |
-   | Content Cell | Content Cell  |
-
-Four spaces is a code block:
-
-    First Header | Second Header
-    ------------ | -------------
-    Content Cell | Content Cell
-    Content Cell | Content Cell
-
-| First Header | Second Header |
-| ------------ | ------------- |
-
-More inline code block tests
-
-Column 1 | Column 2 | Column 3
----------|----------|---------
-word 1   | word 2   | word 3
-word 1   | `word 2` | word 3
-word 1   | \`word 2 | word 3
-word 1   | `word 2 | word 3
-word 1   | `word |2` | word 3
-words    |`` some | code `` | more words
-words    |``` some | code ``` | more words
-words    |```` some | code ```` | more words
-words    |`` some ` | ` code `` | more words
-words    |``` some ` | ` code ``` | more words
-words    |```` some ` | ` code ```` | more words
-
-A test for issue #440:
-
-foo | bar
---- | ---
-foo | (`bar`) and `baz`.
-
-Lists are not tables
-
- - this | should | not
- - be | a | table
-
-Add tests for issue #449
-
-Odd backticks | Even backticks
------------- | -------------
-``[!\"\#$%&'()*+,\-./:;<=>?@\[\\\]^_`{|}~]`` | ``[!\"\#$%&'()*+,\-./:;<=>?@\[\\\]^`_`{|}~]``
-
-Escapes | More Escapes
-------- | ------
-`` `\`` | `\`
-
-Only the first backtick can be escaped
-
-Escaped | Bacticks
-------- | ------
-\`` \`  | \`\`
-
-Test escaped pipes
-
-Column 1 | Column 2
--------- | --------
-`|` \|   | Pipes are okay in code and escaped. \|
-
-| Column 1 | Column 2 |
-| -------- | -------- |
-| row1     | row1    \|
-| row2     | row2     |
-
-Test header escapes
-
-| `` `\`` \| | `\` \|
-| ---------- | ---- |
-| row1       | row1 |
-| row2       | row2 |
-
-Escaped pipes in format row should not be a table
-
-| Column1   | Column2 |
-| ------- \|| ------- |
-| row1      | row1    |
-| row2      | row2    |
-
-Test escaped code in Table
-
-Should not be code | Should be code
------------------- | --------------
-\`Not code\`       | \\`code`
-\\\`Not code\\\`   | \\\\`code`
-
-Single column tables
-
-| Is a Table |
-| ---------- |
-
-| Is a Table
-| ----------
-
-Is a Table |
----------- |
-
-| Is a Table |
-| ---------- |
-| row        |
-
-| Is a Table
-| ----------
-| row
-
-Is a Table |
----------- |
-row        |
-
-| Is not a Table
---------------
-| row
-
-Is not a Table |
---------------
-row            |
-
-| Is not a Table
-| --------------
-row
-
-Is not a Table |
--------------- |
-row
diff --git a/tests/test_legacy.py b/tests/test_legacy.py
index 363161a..62bc075 100644
--- a/tests/test_legacy.py
+++ b/tests/test_legacy.py
@@ -182,8 +182,6 @@ class TestExtensionsExtra(LegacyTestCase):
 
     footnotes = Kwargs(extensions=['footnotes'])
 
-    tables = Kwargs(extensions=['tables'])
-
     extra_config = Kwargs(
         extensions=['extra'],
         extension_configs={
diff --git a/tests/test_syntax/extensions/test_tables.py b/tests/test_syntax/extensions/test_tables.py
index b01ea0c..cd3fbe4 100644
--- a/tests/test_syntax/extensions/test_tables.py
+++ b/tests/test_syntax/extensions/test_tables.py
@@ -20,6 +20,7 @@ License: BSD (see LICENSE.md for details).
 """
 
 from markdown.test_tools import TestCase
+from markdown.extensions.tables import TableExtension
 
 
 class TestTableBlocks(TestCase):
@@ -60,3 +61,862 @@ Content Cell  |  
             ),
             extensions=['tables']
         )
+
+    def test_no_sides(self):
+        self.assertMarkdownRenders(
+            self.dedent(
+                """
+                First Header  | Second Header
+                ------------- | -------------
+                Content Cell  | Content Cell
+                Content Cell  | Content Cell
+                """
+            ),
+            self.dedent(
+                """
+                <table>
+                <thead>
+                <tr>
+                <th>First Header</th>
+                <th>Second Header</th>
+                </tr>
+                </thead>
+                <tbody>
+                <tr>
+                <td>Content Cell</td>
+                <td>Content Cell</td>
+                </tr>
+                <tr>
+                <td>Content Cell</td>
+                <td>Content Cell</td>
+                </tr>
+                </tbody>
+                </table>
+                """
+            ),
+            extensions=['tables']
+        )
+
+    def test_both_sides(self):
+        self.assertMarkdownRenders(
+            self.dedent(
+                """
+                | First Header  | Second Header |
+                | ------------- | ------------- |
+                | Content Cell  | Content Cell  |
+                | Content Cell  | Content Cell  |
+                """
+            ),
+            self.dedent(
+                """
+                <table>
+                <thead>
+                <tr>
+                <th>First Header</th>
+                <th>Second Header</th>
+                </tr>
+                </thead>
+                <tbody>
+                <tr>
+                <td>Content Cell</td>
+                <td>Content Cell</td>
+                </tr>
+                <tr>
+                <td>Content Cell</td>
+                <td>Content Cell</td>
+                </tr>
+                </tbody>
+                </table>
+                """
+            ),
+            extensions=['tables']
+        )
+
+    def test_align_columns(self):
+        self.assertMarkdownRenders(
+            self.dedent(
+                """
+                | Item      | Value |
+                | :-------- | -----:|
+                | Computer  | $1600 |
+                | Phone     |   $12 |
+                | Pipe      |    $1 |
+                """
+            ),
+            self.dedent(
+                """
+                <table>
+                <thead>
+                <tr>
+                <th style="text-align: left;">Item</th>
+                <th style="text-align: right;">Value</th>
+                </tr>
+                </thead>
+                <tbody>
+                <tr>
+                <td style="text-align: left;">Computer</td>
+                <td style="text-align: right;">$1600</td>
+                </tr>
+                <tr>
+                <td style="text-align: left;">Phone</td>
+                <td style="text-align: right;">$12</td>
+                </tr>
+                <tr>
+                <td style="text-align: left;">Pipe</td>
+                <td style="text-align: right;">$1</td>
+                </tr>
+                </tbody>
+                </table>
+                """
+            ),
+            extensions=['tables']
+        )
+
+    def test_styles_in_tables(self):
+        self.assertMarkdownRenders(
+            self.dedent(
+                """
+                | Function name | Description                    |
+                | ------------- | ------------------------------ |
+                | `help()`      | Display the help window.       |
+                | `destroy()`   | **Destroy your computer!**     |
+                """
+            ),
+            self.dedent(
+                """
+                <table>
+                <thead>
+                <tr>
+                <th>Function name</th>
+                <th>Description</th>
+                </tr>
+                </thead>
+                <tbody>
+                <tr>
+                <td><code>help()</code></td>
+                <td>Display the help window.</td>
+                </tr>
+                <tr>
+                <td><code>destroy()</code></td>
+                <td><strong>Destroy your computer!</strong></td>
+                </tr>
+                </tbody>
+                </table>
+                """
+            ),
+            extensions=['tables']
+        )
+
+    def test_align_three(self):
+        self.assertMarkdownRenders(
+            self.dedent(
+                """
+                |foo|bar|baz|
+                |:--|:-:|--:|
+                |   | Q |   |
+                |W  |   |  W|
+                """
+            ),
+            self.dedent(
+                """
+                <table>
+                <thead>
+                <tr>
+                <th style="text-align: left;">foo</th>
+                <th style="text-align: center;">bar</th>
+                <th style="text-align: right;">baz</th>
+                </tr>
+                </thead>
+                <tbody>
+                <tr>
+                <td style="text-align: left;"></td>
+                <td style="text-align: center;">Q</td>
+                <td style="text-align: right;"></td>
+                </tr>
+                <tr>
+                <td style="text-align: left;">W</td>
+                <td style="text-align: center;"></td>
+                <td style="text-align: right;">W</td>
+                </tr>
+                </tbody>
+                </table>
+                """
+            ),
+            extensions=['tables']
+        )
+
+    def test_three_columns(self):
+        self.assertMarkdownRenders(
+            self.dedent(
+                """
+                foo|bar|baz
+                ---|---|---
+                   | Q |
+                 W |   | W
+                """
+            ),
+            self.dedent(
+                """
+                <table>
+                <thead>
+                <tr>
+                <th>foo</th>
+                <th>bar</th>
+                <th>baz</th>
+                </tr>
+                </thead>
+                <tbody>
+                <tr>
+                <td></td>
+                <td>Q</td>
+                <td></td>
+                </tr>
+                <tr>
+                <td>W</td>
+                <td></td>
+                <td>W</td>
+                </tr>
+                </tbody>
+                </table>
+                """
+            ),
+            extensions=['tables']
+        )
+
+    def test_three_spaces_prefix(self):
+        self.assertMarkdownRenders(
+            self.dedent(
+                """
+                Three spaces in front of a table:
+
+                   First Header | Second Header
+                   ------------ | -------------
+                   Content Cell | Content Cell
+                   Content Cell | Content Cell
+
+                   | First Header | Second Header |
+                   | ------------ | ------------- |
+                   | Content Cell | Content Cell  |
+                   | Content Cell | Content Cell  |
+                """),
+            self.dedent(
+                """
+                <p>Three spaces in front of a table:</p>
+                <table>
+                <thead>
+                <tr>
+                <th>First Header</th>
+                <th>Second Header</th>
+                </tr>
+                </thead>
+                <tbody>
+                <tr>
+                <td>Content Cell</td>
+                <td>Content Cell</td>
+                </tr>
+                <tr>
+                <td>Content Cell</td>
+                <td>Content Cell</td>
+                </tr>
+                </tbody>
+                </table>
+                <table>
+                <thead>
+                <tr>
+                <th>First Header</th>
+                <th>Second Header</th>
+                </tr>
+                </thead>
+                <tbody>
+                <tr>
+                <td>Content Cell</td>
+                <td>Content Cell</td>
+                </tr>
+                <tr>
+                <td>Content Cell</td>
+                <td>Content Cell</td>
+                </tr>
+                </tbody>
+                </table>
+                """
+            ),
+            extensions=['tables']
+        )
+
+    def test_code_block_table(self):
+        self.assertMarkdownRenders(
+            self.dedent(
+                """
+                Four spaces is a code block:
+
+                    First Header | Second Header
+                    ------------ | -------------
+                    Content Cell | Content Cell
+                    Content Cell | Content Cell
+
+                | First Header | Second Header |
+                | ------------ | ------------- |
+                """),
+            self.dedent(
+                """
+                <p>Four spaces is a code block:</p>
+                <pre><code>First Header | Second Header
+                ------------ | -------------
+                Content Cell | Content Cell
+                Content Cell | Content Cell
+                </code></pre>
+                <table>
+                <thead>
+                <tr>
+                <th>First Header</th>
+                <th>Second Header</th>
+                </tr>
+                </thead>
+                <tbody>
+                <tr>
+                <td></td>
+                <td></td>
+                </tr>
+                </tbody>
+                </table>
+                """
+            ),
+            extensions=['tables']
+        )
+
+    def test_inline_code_blocks(self):
+        self.assertMarkdownRenders(
+            self.dedent(
+                """
+                More inline code block tests
+
+                Column 1 | Column 2 | Column 3
+                ---------|----------|---------
+                word 1   | word 2   | word 3
+                word 1   | `word 2` | word 3
+                word 1   | \\`word 2 | word 3
+                word 1   | `word 2 | word 3
+                word 1   | `word |2` | word 3
+                words    |`` some | code `` | more words
+                words    |``` some | code ``` | more words
+                words    |```` some | code ```` | more words
+                words    |`` some ` | ` code `` | more words
+                words    |``` some ` | ` code ``` | more words
+                words    |```` some ` | ` code ```` | more words
+                """),
+            self.dedent(
+                """
+                <p>More inline code block tests</p>
+                <table>
+                <thead>
+                <tr>
+                <th>Column 1</th>
+                <th>Column 2</th>
+                <th>Column 3</th>
+                </tr>
+                </thead>
+                <tbody>
+                <tr>
+                <td>word 1</td>
+                <td>word 2</td>
+                <td>word 3</td>
+                </tr>
+                <tr>
+                <td>word 1</td>
+                <td><code>word 2</code></td>
+                <td>word 3</td>
+                </tr>
+                <tr>
+                <td>word 1</td>
+                <td>`word 2</td>
+                <td>word 3</td>
+                </tr>
+                <tr>
+                <td>word 1</td>
+                <td>`word 2</td>
+                <td>word 3</td>
+                </tr>
+                <tr>
+                <td>word 1</td>
+                <td><code>word |2</code></td>
+                <td>word 3</td>
+                </tr>
+                <tr>
+                <td>words</td>
+                <td><code>some | code</code></td>
+                <td>more words</td>
+                </tr>
+                <tr>
+                <td>words</td>
+                <td><code>some | code</code></td>
+                <td>more words</td>
+                </tr>
+                <tr>
+                <td>words</td>
+                <td><code>some | code</code></td>
+                <td>more words</td>
+                </tr>
+                <tr>
+                <td>words</td>
+                <td><code>some ` | ` code</code></td>
+                <td>more words</td>
+                </tr>
+                <tr>
+                <td>words</td>
+                <td><code>some ` | ` code</code></td>
+                <td>more words</td>
+                </tr>
+                <tr>
+                <td>words</td>
+                <td><code>some ` | ` code</code></td>
+                <td>more words</td>
+                </tr>
+                </tbody>
+                </table>
+                """
+            ),
+            extensions=['tables']
+        )
+
+    def test_issue_440(self):
+        self.assertMarkdownRenders(
+            self.dedent(
+                """
+                A test for issue #440:
+
+                foo | bar
+                --- | ---
+                foo | (`bar`) and `baz`.
+                """),
+            self.dedent(
+                """
+                <p>A test for issue #440:</p>
+                <table>
+                <thead>
+                <tr>
+                <th>foo</th>
+                <th>bar</th>
+                </tr>
+                </thead>
+                <tbody>
+                <tr>
+                <td>foo</td>
+                <td>(<code>bar</code>) and <code>baz</code>.</td>
+                </tr>
+                </tbody>
+                </table>
+                """
+            ),
+            extensions=['tables']
+        )
+
+    def test_lists_not_tables(self):
+        self.assertMarkdownRenders(
+            self.dedent(
+                """
+                Lists are not tables
+
+                 - this | should | not
+                 - be | a | table
+                """),
+            self.dedent(
+                """
+                <p>Lists are not tables</p>
+                <ul>
+                <li>this | should | not</li>
+                <li>be | a | table</li>
+                </ul>
+                """
+            ),
+            extensions=['tables']
+        )
+
+    def test_issue_449(self):
+        self.assertMarkdownRenders(
+            self.dedent(
+                r"""
+                Add tests for issue #449
+
+                Odd backticks | Even backticks
+                ------------ | -------------
+                ``[!\"\#$%&'()*+,\-./:;<=>?@\[\\\]^_`{|}~]`` | ``[!\"\#$%&'()*+,\-./:;<=>?@\[\\\]^`_`{|}~]``
+
+                Escapes | More Escapes
+                ------- | ------
+                `` `\`` | `\`
+
+                Only the first backtick can be escaped
+
+                Escaped | Bacticks
+                ------- | ------
+                \`` \`  | \`\`
+
+                Test escaped pipes
+
+                Column 1 | Column 2
+                -------- | --------
+                `|` \|   | Pipes are okay in code and escaped. \|
+
+                | Column 1 | Column 2 |
+                | -------- | -------- |
+                | row1     | row1    \|
+                | row2     | row2     |
+
+                Test header escapes
+
+                | `` `\`` \| | `\` \|
+                | ---------- | ---- |
+                | row1       | row1 |
+                | row2       | row2 |
+
+                Escaped pipes in format row should not be a table
+
+                | Column1   | Column2 |
+                | ------- \|| ------- |
+                | row1      | row1    |
+                | row2      | row2    |
+
+                Test escaped code in Table
+
+                Should not be code | Should be code
+                ------------------ | --------------
+                \`Not code\`       | \\`code`
+                \\\`Not code\\\`   | \\\\`code`
+                """),
+            self.dedent(
+                """
+                <p>Add tests for issue #449</p>
+                <table>
+                <thead>
+                <tr>
+                <th>Odd backticks</th>
+                <th>Even backticks</th>
+                </tr>
+                </thead>
+                <tbody>
+                <tr>
+                <td><code>[!\\"\\#$%&amp;'()*+,\\-./:;&lt;=&gt;?@\\[\\\\\\]^_`{|}~]</code></td>
+                <td><code>[!\\"\\#$%&amp;'()*+,\\-./:;&lt;=&gt;?@\\[\\\\\\]^`_`{|}~]</code></td>
+                </tr>
+                </tbody>
+                </table>
+                <table>
+                <thead>
+                <tr>
+                <th>Escapes</th>
+                <th>More Escapes</th>
+                </tr>
+                </thead>
+                <tbody>
+                <tr>
+                <td><code>`\\</code></td>
+                <td><code>\\</code></td>
+                </tr>
+                </tbody>
+                </table>
+                <p>Only the first backtick can be escaped</p>
+                <table>
+                <thead>
+                <tr>
+                <th>Escaped</th>
+                <th>Bacticks</th>
+                </tr>
+                </thead>
+                <tbody>
+                <tr>
+                <td>`<code>\\</code></td>
+                <td>``</td>
+                </tr>
+                </tbody>
+                </table>
+                <p>Test escaped pipes</p>
+                <table>
+                <thead>
+                <tr>
+                <th>Column 1</th>
+                <th>Column 2</th>
+                </tr>
+                </thead>
+                <tbody>
+                <tr>
+                <td><code>|</code> |</td>
+                <td>Pipes are okay in code and escaped. |</td>
+                </tr>
+                </tbody>
+                </table>
+                <table>
+                <thead>
+                <tr>
+                <th>Column 1</th>
+                <th>Column 2</th>
+                </tr>
+                </thead>
+                <tbody>
+                <tr>
+                <td>row1</td>
+                <td>row1    |</td>
+                </tr>
+                <tr>
+                <td>row2</td>
+                <td>row2</td>
+                </tr>
+                </tbody>
+                </table>
+                <p>Test header escapes</p>
+                <table>
+                <thead>
+                <tr>
+                <th><code>`\\</code> |</th>
+                <th><code>\\</code> |</th>
+                </tr>
+                </thead>
+                <tbody>
+                <tr>
+                <td>row1</td>
+                <td>row1</td>
+                </tr>
+                <tr>
+                <td>row2</td>
+                <td>row2</td>
+                </tr>
+                </tbody>
+                </table>
+                <p>Escaped pipes in format row should not be a table</p>
+                <p>| Column1   | Column2 |
+                | ------- || ------- |
+                | row1      | row1    |
+                | row2      | row2    |</p>
+                <p>Test escaped code in Table</p>
+                <table>
+                <thead>
+                <tr>
+                <th>Should not be code</th>
+                <th>Should be code</th>
+                </tr>
+                </thead>
+                <tbody>
+                <tr>
+                <td>`Not code`</td>
+                <td>\\<code>code</code></td>
+                </tr>
+                <tr>
+                <td>\\`Not code\\`</td>
+                <td>\\\\<code>code</code></td>
+                </tr>
+                </tbody>
+                </table>
+                """
+            ),
+            extensions=['tables']
+        )
+
+    def test_single_column_tables(self):
+        self.assertMarkdownRenders(
+            self.dedent(
+                """
+                Single column tables
+
+                | Is a Table |
+                | ---------- |
+
+                | Is a Table
+                | ----------
+
+                Is a Table |
+                ---------- |
+
+                | Is a Table |
+                | ---------- |
+                | row        |
+
+                | Is a Table
+                | ----------
+                | row
+
+                Is a Table |
+                ---------- |
+                row        |
+
+                | Is not a Table
+                --------------
+                | row
+
+                Is not a Table |
+                --------------
+                row            |
+
+                | Is not a Table
+                | --------------
+                row
+
+                Is not a Table |
+                -------------- |
+                row
+                """),
+            self.dedent(
+                """
+                <p>Single column tables</p>
+                <table>
+                <thead>
+                <tr>
+                <th>Is a Table</th>
+                </tr>
+                </thead>
+                <tbody>
+                <tr>
+                <td></td>
+                </tr>
+                </tbody>
+                </table>
+                <table>
+                <thead>
+                <tr>
+                <th>Is a Table</th>
+                </tr>
+                </thead>
+                <tbody>
+                <tr>
+                <td></td>
+                </tr>
+                </tbody>
+                </table>
+                <table>
+                <thead>
+                <tr>
+                <th>Is a Table</th>
+                </tr>
+                </thead>
+                <tbody>
+                <tr>
+                <td></td>
+                </tr>
+                </tbody>
+                </table>
+                <table>
+                <thead>
+                <tr>
+                <th>Is a Table</th>
+                </tr>
+                </thead>
+                <tbody>
+                <tr>
+                <td>row</td>
+                </tr>
+                </tbody>
+                </table>
+                <table>
+                <thead>
+                <tr>
+                <th>Is a Table</th>
+                </tr>
+                </thead>
+                <tbody>
+                <tr>
+                <td>row</td>
+                </tr>
+                </tbody>
+                </table>
+                <table>
+                <thead>
+                <tr>
+                <th>Is a Table</th>
+                </tr>
+                </thead>
+                <tbody>
+                <tr>
+                <td>row</td>
+                </tr>
+                </tbody>
+                </table>
+                <h2>| Is not a Table</h2>
+                <p>| row</p>
+                <h2>Is not a Table |</h2>
+                <p>row            |</p>
+                <p>| Is not a Table
+                | --------------
+                row</p>
+                <p>Is not a Table |
+                -------------- |
+                row</p>
+                """
+            ),
+            extensions=['tables']
+        )
+
+    def test_align_columns_legacy(self):
+        self.assertMarkdownRenders(
+            self.dedent(
+                """
+                | Item      | Value |
+                | :-------- | -----:|
+                | Computer  | $1600 |
+                | Phone     |   $12 |
+                | Pipe      |    $1 |
+                """
+            ),
+            self.dedent(
+                """
+                <table>
+                <thead>
+                <tr>
+                <th align="left">Item</th>
+                <th align="right">Value</th>
+                </tr>
+                </thead>
+                <tbody>
+                <tr>
+                <td align="left">Computer</td>
+                <td align="right">$1600</td>
+                </tr>
+                <tr>
+                <td align="left">Phone</td>
+                <td align="right">$12</td>
+                </tr>
+                <tr>
+                <td align="left">Pipe</td>
+                <td align="right">$1</td>
+                </tr>
+                </tbody>
+                </table>
+                """
+            ),
+            extensions=[TableExtension(use_align_attribute=True)]
+        )
+
+    def test_align_three_legacy(self):
+        self.assertMarkdownRenders(
+            self.dedent(
+                """
+                |foo|bar|baz|
+                |:--|:-:|--:|
+                |   | Q |   |
+                |W  |   |  W|
+                """
+            ),
+            self.dedent(
+                """
+                <table>
+                <thead>
+                <tr>
+                <th align="left">foo</th>
+                <th align="center">bar</th>
+                <th align="right">baz</th>
+                </tr>
+                </thead>
+                <tbody>
+                <tr>
+                <td align="left"></td>
+                <td align="center">Q</td>
+                <td align="right"></td>
+                </tr>
+                <tr>
+                <td align="left">W</td>
+                <td align="center"></td>
+                <td align="right">W</td>
+                </tr>
+                </tbody>
+                </table>
+                """
+            ),
+            extensions=[TableExtension(use_align_attribute=True)]
+        )