diff --git a/novel_stats/novel_stats.py b/novel_stats/novel_stats.py
index efc3aba..6f66893 100755
--- a/novel_stats/novel_stats.py
+++ b/novel_stats/novel_stats.py
@@ -3,12 +3,13 @@
 
 import collections
 import sys
-
+import tempfile
 
 CHAPTER_MARKER = '## '
 STATUS_MARKER = '[status]: # '
 ACT_MARKER = '[act]: # '
-COMMENT_MARKER = '[//]: # ' # Strandard markdown comment marker, supported by pandoc and calibre's ebook-convert
+# Standard markdown comment marker, supported by Pandoc and Calibre's ebook-convert.
+COMMENT_MARKER = '[//]: # '
 
 
 def count_words(line):
@@ -31,7 +32,8 @@ def main():
     if '-pp' in arguments:
         # -pp flag to allow Markdown Preprocessing primarily to allow multi-file novel formatting
         # this is implemented using a temporary file created using python's buit-in tempfile library
-        import MarkdownPP, tempfile
+        import MarkdownPP
+
         mdfile = tempfile.TemporaryFile(mode='w+')
         MarkdownPP.MarkdownPP(input=open(filename), output=mdfile, modules=list(MarkdownPP.modules))
         mdfile.seek(0)
@@ -52,22 +54,24 @@ def main():
             word_count_by_act[act_heading] += word_count_by_chapter[chapter_heading]
             total_word_count += word_count_by_chapter[chapter_heading]
 
-            chapter_heading = line[len(CHAPTER_MARKER):].strip('()\n')
+            chapter_heading = line[len(CHAPTER_MARKER) :].strip('()\n')
 
-            word_count_by_chapter[chapter_heading] = count_words(chapter_heading)  # Count the words in chapter heading, because the chapter number and title count as words.
+            # Count the words in chapter heading, because the chapter number and title count as words.
+            word_count_by_chapter[chapter_heading] = count_words(chapter_heading)
 
             status_by_chapter[chapter_heading] = collections.defaultdict(int)
             current_status = None
-        elif line.startswith(STATUS_MARKER): # Modified to allow multiple statuses in a single chapter, can swap back and forth.
-            if current_status == None:
-                current_status = line[len(STATUS_MARKER):].strip('()\n')
+        # Modified to allow multiple statuses in a single chapter, can swap back and forth.
+        elif line.startswith(STATUS_MARKER):
+            if current_status is None:
+                current_status = line[len(STATUS_MARKER) :].strip('()\n')
                 status_by_chapter[chapter_heading][current_status] = count_words(chapter_heading)
             else:
-                current_status = line[len(STATUS_MARKER):].strip('()\n')
+                current_status = line[len(STATUS_MARKER) :].strip('()\n')
         elif line.startswith(ACT_MARKER):
-            act_heading = line[len(ACT_MARKER):].strip('()\n')
+            act_heading = line[len(ACT_MARKER) :].strip('()\n')
             word_count_by_act[act_heading] = count_words(act_heading)
-        elif line.startswith(COMMENT_MARKER): # don't count the words in a comment
+        elif line.startswith(COMMENT_MARKER):  # Don't count the words in a comment.
             pass
         else:
             line_word_count = count_words(line)
@@ -83,7 +87,8 @@ def main():
     word_count_by_act[act_heading] += word_count_by_chapter[chapter_heading]
     total_word_count += word_count_by_chapter[chapter_heading]
 
-    if '-c' in arguments or '--chapter' in arguments: # -c or --chapter to give a chapter-by-chapter word count summary
+    # -c or --chapter to give a chapter-by-chapter word count summary.
+    if '-c' in arguments or '--chapter' in arguments:
         for chapter_heading, chapter_word_count in word_count_by_chapter.items():
             if chapter_heading is None:
                 continue
@@ -102,17 +107,24 @@ def main():
 
         print()
 
-    if '-a' in arguments or '--act' in arguments: # -a or --act to give an act-by-act word count summary
+    # -a or --act to give an act-by-act word count summary.
+    if '-a' in arguments or '--act' in arguments:
         for act_heading, act_word_count in word_count_by_act.items():
             if act_heading is None:
                 continue
 
-            print('act {}: {:,} words (~{}%)'.format(act_heading, act_word_count, act_word_count * 100 // total_word_count))
+            print(
+                'act {}: {:,} words (~{}%)'.format(
+                    act_heading, act_word_count, act_word_count * 100 // total_word_count
+                )
+            )
 
         print()
 
     for status, status_word_count in word_count_by_status.items():
-        print(f'{status}: {status_word_count:,} words (~{status_word_count * 100 // total_word_count}%)')
+        print(
+            f'{status}: {status_word_count:,} words (~{status_word_count * 100 // total_word_count}%)'
+        )
 
     print(f'total: {total_word_count:,} words')
 
diff --git a/pyproject.toml b/pyproject.toml
new file mode 100644
index 0000000..10572da
--- /dev/null
+++ b/pyproject.toml
@@ -0,0 +1,3 @@
+[tool.black]
+line-length = 100
+skip-string-normalization = true
diff --git a/setup.cfg b/setup.cfg
new file mode 100644
index 0000000..f6bed47
--- /dev/null
+++ b/setup.cfg
@@ -0,0 +1,20 @@
+[metadata]
+description_file=README.md
+
+[tool:pytest]
+testpaths = tests
+addopts = --cov-report term-missing:skip-covered --cov=novel_stats
+filterwarnings = 
+    ignore:Coverage disabled.*:pytest.PytestWarning
+
+[flake8]
+ignore = E203,E501,W503
+exclude = *.*/*
+
+[tool:isort]
+force_single_line = False
+include_trailing_comma = True
+known_first_party = novel_stats
+line_length = 100
+multi_line_output = 3
+skip = .tox
diff --git a/setup.py b/setup.py
index 58108d7..9b7f29b 100644
--- a/setup.py
+++ b/setup.py
@@ -1,33 +1,27 @@
 from setuptools import find_packages, setup
 
-VERSION = '0.1.0'
+VERSION = "0.1.0"
 
 
 setup(
-    name='novel-stats',
+    name="novel-stats",
     version=VERSION,
-    description='Produce word count statistics for novels written in Markdown format.',
-    author='Dan Helfman',
-    author_email='witten@torsion.org',
-    url='https://projects.torsion.org/witten/novel-stats',
+    description="Produce word count statistics for novels written in Markdown format.",
+    author="Dan Helfman",
+    author_email="witten@torsion.org",
+    url="https://projects.torsion.org/witten/novel-stats",
     classifiers=[
-        'Development Status :: 4 - Beta',
-        'Environment :: Console',
-        'Intended Audience :: Other Audience',
-        'License :: OSI Approved :: GNU General Public License v3 (GPLv3)',
-        'Programming Language :: Python',
-        'Topic :: Office/Business',
-        'Topic :: Text Processing :: Markup',
+        "Development Status :: 4 - Beta",
+        "Environment :: Console",
+        "Intended Audience :: Other Audience",
+        "License :: OSI Approved :: GNU General Public License v3 (GPLv3)",
+        "Programming Language :: Python",
+        "Topic :: Office/Business",
+        "Topic :: Text Processing :: Markup",
     ],
-    packages=find_packages(exclude=['tests*']),
-    entry_points={
-        'console_scripts': [
-            'novel-stats = novel_stats.novel_stats:main',
-        ]
-    },
+    packages=find_packages(exclude=["tests*"]),
+    entry_points={"console_scripts": ["novel-stats = novel_stats.novel_stats:main",]},
     install_requires=(),
-    extras_require = {
-        'multi_file': ['MarkdownPP'],
-    },
+    extras_require={"multi_file": ["MarkdownPP"],},
     include_package_data=True,
 )
diff --git a/test_requirements.txt b/test_requirements.txt
new file mode 100644
index 0000000..bee04f4
--- /dev/null
+++ b/test_requirements.txt
@@ -0,0 +1,18 @@
+appdirs==1.4.4; python_version >= '3.8'
+attrs==20.3.0; python_version >= '3.8'
+black==19.10b0; python_version >= '3.8'
+click==7.1.2; python_version >= '3.8'
+coverage==5.3
+flake8==3.8.4
+flexmock==0.10.4
+isort==5.9.1
+mccabe==0.6.1
+pluggy==0.13.1
+pathspec==0.8.1; python_version >= '3.8'
+py==1.10.0
+pycodestyle==2.6.0
+pyflakes==2.2.0
+pytest==6.1.2
+pytest-cov==2.10.1
+regex; python_version >= '3.8'
+typed-ast==1.4.2; python_version >= '3.8'
diff --git a/tests/test_novel_stats.py b/tests/test_novel_stats.py
new file mode 100644
index 0000000..e041d58
--- /dev/null
+++ b/tests/test_novel_stats.py
@@ -0,0 +1,17 @@
+from novel_stats import novel_stats as module
+
+
+def test_count_words_tallies_basic_sentence():
+    assert module.count_words('This sentence is five words.') == 5
+
+
+def test_count_words_em_dash_does_not_split_words():
+    assert module.count_words('This is only six—or is it?') == 6
+
+
+def test_count_words_skips_chapter_marker():
+    assert module.count_words('## Chapter 1') == 2
+
+
+def test_count_words_skips_scene_break():
+    assert module.count_words('* * *') == 0
diff --git a/tox.ini b/tox.ini
new file mode 100644
index 0000000..a2146c4
--- /dev/null
+++ b/tox.ini
@@ -0,0 +1,28 @@
+[tox]
+envlist = py36,py37,py38,py39
+skip_missing_interpreters = True
+skipsdist = True
+minversion = 3.14.1
+
+[testenv]
+usedevelop = True
+deps = -rtest_requirements.txt
+passenv = COVERAGE_FILE
+commands =
+    pytest {posargs}
+    py38,py39: black --check .
+    isort --check-only --settings-path setup.cfg .
+    flake8 novel_stats tests
+
+[testenv:black]
+commands =
+    black {posargs} .
+
+[testenv:test]
+commands =
+    pytest {posargs}
+
+[testenv:isort]
+deps = {[testenv]deps}
+commands =
+    isort --settings-path setup.cfg .