diff --git a/lib/unexpected-magicpen.js b/lib/unexpected-magicpen.js
index f75b6d2..0209a44 100644
--- a/lib/unexpected-magicpen.js
+++ b/lib/unexpected-magicpen.js
@@ -1,170 +1,189 @@
 module.exports = {
-    name: 'unexpected-magicpen',
-    version: require('../package.json').version,
-    installInto: function unexpectedMagicPen(expect) {
-        expect.addType({
-            name: 'magicpen',
-            identify: function (obj) {
-                return obj && obj.isMagicPen;
-            },
-            inspect: function (pen, depth, output) {
-                output.magicPen(pen);
-            },
-            equal: function (a, b) {
-                if (a.format !== b.format) {
-                    return false;
-                }
-                if (a.format) {
-                    // Both have the same format
-                    return a.toString() === b.toString();
-                } else {
-                    // Neither have a format, test all serializations
-                    return a.toString() === b.toString() &&
-                        a.toString('ansi') === b.toString('ansi') &&
-                        a.toString('html') === b.toString('html');
-                }
+  name: 'unexpected-magicpen',
+  version: require('../package.json').version,
+  installInto: function unexpectedMagicPen(expect) {
+    expect.addType({
+      name: 'magicpen',
+      identify: function (obj) {
+        return obj && obj.isMagicPen;
+      },
+      inspect: function (pen, depth, output) {
+        output.magicPen(pen);
+      },
+      equal: function (a, b) {
+        if (a.format !== b.format) {
+          return false;
+        }
+        if (a.format) {
+          // Both have the same format
+          return a.toString() === b.toString();
+        } else {
+          // Neither have a format, test all serializations
+          return (
+            a.toString() === b.toString() &&
+            a.toString('ansi') === b.toString('ansi') &&
+            a.toString('html') === b.toString('html')
+          );
+        }
+      },
+    });
+
+    expect.addStyle('magicPenLine', function (line, pen) {
+      line.forEach(function (lineEntry, j) {
+        if (j > 0) {
+          this.nl();
+        }
+        if (lineEntry.style === 'text') {
+          var styles = lineEntry.args.styles;
+          if (
+            pen &&
+            styles.length === 1 &&
+            typeof pen[styles[0]] === 'function'
+          ) {
+            // Text with a single style also available as a method on the pen being inspected:
+            this.text('.')
+              .jsFunctionName(styles[0])
+              .text('(')
+              .singleQuotedString(lineEntry.args.content)
+              .text(')');
+          } else {
+            this.text('.')
+              .jsFunctionName('text')
+              .text('(')
+              .singleQuotedString(lineEntry.args.content);
+            if (styles.length > 0) {
+              this.text(', ').appendInspected(
+                styles.length === 1 && Array.isArray(styles[0])
+                  ? styles[0]
+                  : styles
+              );
             }
-        });
+            this.text(')');
+          }
+        } else if (lineEntry.style === 'raw') {
+          this.text('.')
+            .jsFunctionName('raw')
+            .text('(')
+            .appendInspected(lineEntry.args.content())
+            .text(')');
+        } else {
+          // lineEntry.style === 'block'
+          this.text('.')
+            .jsFunctionName('block')
+            .text('(')
+            .jsKeyword('function')
+            .text(' () {');
+          if (
+            lineEntry.args &&
+            lineEntry.args.length > 0 &&
+            lineEntry.args[0] &&
+            lineEntry.args[0].length > 0
+          ) {
+            this.nl()
+              .indentLines()
+              .i()
+              .magicPen(pen, lineEntry.args)
+              .outdentLines()
+              .nl();
+          }
+          this.text('})');
+        }
+      }, this);
+    });
 
-        expect.addStyle('magicPenLine', function (line, pen) {
-            line.forEach(function (lineEntry, j) {
-                if (j > 0) {
-                    this.nl();
-                }
-                if (lineEntry.style === 'text') {
-                    var styles = lineEntry.args.styles;
-                    if (pen && styles.length === 1 && typeof pen[styles[0]] === 'function') {
-                        // Text with a single style also available as a method on the pen being inspected:
-                        this
-                            .text('.')
-                            .jsFunctionName(styles[0])
-                            .text('(')
-                            .singleQuotedString(lineEntry.args.content)
-                            .text(')');
-                    } else {
-                        this
-                            .text('.')
-                            .jsFunctionName('text')
-                            .text('(')
-                            .singleQuotedString(lineEntry.args.content);
-                        if (styles.length > 0) {
-                            this
-                                .text(', ')
-                                .appendInspected(styles.length === 1 && Array.isArray(styles[0]) ? styles[0] : styles);
-                        }
-                        this.text(')');
-                    }
-                } else if (lineEntry.style === 'raw') {
-                    this
-                        .text('.')
-                        .jsFunctionName('raw')
-                        .text('(')
-                        .appendInspected(lineEntry.args.content())
-                        .text(')');
-                } else {
-                    // lineEntry.style === 'block'
-                    this
-                        .text('.')
-                        .jsFunctionName('block').text('(').jsKeyword('function').text(' () {');
-                    if (lineEntry.args && lineEntry.args.length > 0 && lineEntry.args[0] && lineEntry.args[0].length > 0) {
-                        this
-                            .nl()
-                            .indentLines()
-                            .i()
-                            .magicPen(pen, lineEntry.args)
-                            .outdentLines()
-                            .nl();
-                    }
-                    this.text('})');
-                }
+    expect.addStyle('magicPen', function (pen, lines) {
+      var isTopLevel = !lines;
+      lines = lines || pen.output;
+      this.block(function () {
+        if (isTopLevel) {
+          this.jsFunctionName('magicpen').text('(');
+          if (pen.format) {
+            this.singleQuotedString(pen.format);
+          }
+          this.text(')');
+        } else {
+          this.jsKeyword('this');
+        }
+        if (!pen.isEmpty()) {
+          var inspectOnMultipleLines = lines.length > 1 || lines[0].length > 1;
+          if (inspectOnMultipleLines) {
+            this.nl().indentLines().i();
+          }
+          this.block(function () {
+            lines.forEach(function (line, i) {
+              if (i > 0) {
+                this.text('.').jsFunctionName('nl').text('()').nl();
+              }
+              this.magicPenLine(line, pen);
             }, this);
-        });
-
-        expect.addStyle('magicPen', function (pen, lines) {
-            var isTopLevel = !lines;
-            lines = lines || pen.output;
-            this.block(function () {
-                if (isTopLevel) {
-                    this.jsFunctionName('magicpen').text('(');
-                    if (pen.format) {
-                        this.singleQuotedString(pen.format);
-                    }
-                    this.text(')');
-                } else {
-                    this.jsKeyword('this');
-                }
-                if (!pen.isEmpty()) {
-                    var inspectOnMultipleLines = lines.length > 1 || lines[0].length > 1;
-                    if (inspectOnMultipleLines) {
-                        this
-                            .nl()
-                            .indentLines()
-                            .i();
-                    }
-                    this.block(function () {
-                        lines.forEach(function (line, i) {
-                            if (i > 0) {
-                                this.text('.').jsFunctionName('nl').text('()').nl();
-                            }
-                            this.magicPenLine(line, pen);
-                        }, this);
-                        if (!isTopLevel) {
-                            this.text(';');
-                        }
-                    });
-                    if (inspectOnMultipleLines) {
-                        this.outdentLines();
-                    }
-                }
-            });
-
-            // If we're at the top level of a non-empty pen compatible with the current output,
-            // render the output of the pen in a comment:
-            if (isTopLevel && !pen.isEmpty() && (pen.format === this.format || !pen.format)) {
-                this.sp().commentBlock(pen);
+            if (!isTopLevel) {
+              this.text(';');
             }
-        });
+          });
+          if (inspectOnMultipleLines) {
+            this.outdentLines();
+          }
+        }
+      });
 
-        expect.addAssertion('<Error> to have (ansi|html|text|) (message|diff) <any>', function (expect, subject, value) {
-            expect.errorMode = 'nested';
-            var format = expect.alternations[0] || 'text';
-            var useDiff = expect.alternations[1] === 'diff';
-            if (subject.isUnexpected) {
-                var subjectPen;
-                if (useDiff) {
-                    var diff = subject.getDiff({ format: format });
-                    if (diff) {
-                        subjectPen = diff;
-                    } else {
-                        expect.fail('The UnexpectedError instance does not have a diff');
-                    }
-                } else {
-                    subjectPen = subject.getErrorMessage({ format: format });
-                }
-                var valueType = expect.argTypes[0];
-                if (valueType.is('magicpen')) {
-                    expect(subjectPen, 'to equal', value);
-                } else if (valueType.is('function') && !valueType.is('expect.it')) {
-                    var expectedOutput = expect.createOutput(format);
-                    var returnValue = value.call(expectedOutput, subjectPen.toString());
-                    if (!expectedOutput.isEmpty()) {
-                        // If the function didn't generate any expected output, assume that it ran assertions based on the serialized message
-                        expect(subjectPen, 'to equal', expectedOutput);
-                    }
-                    return returnValue;
-                } else {
-                    return expect(subjectPen.toString(), 'to satisfy', value);
-                }
+      // If we're at the top level of a non-empty pen compatible with the current output,
+      // render the output of the pen in a comment:
+      if (
+        isTopLevel &&
+        !pen.isEmpty() &&
+        (pen.format === this.format || !pen.format)
+      ) {
+        this.sp().commentBlock(pen);
+      }
+    });
+
+    expect.addAssertion(
+      '<Error> to have (ansi|html|text|) (message|diff) <any>',
+      function (expect, subject, value) {
+        expect.errorMode = 'nested';
+        var format = expect.alternations[0] || 'text';
+        var useDiff = expect.alternations[1] === 'diff';
+        if (subject.isUnexpected) {
+          var subjectPen;
+          if (useDiff) {
+            var diff = subject.getDiff({ format: format });
+            if (diff) {
+              subjectPen = diff;
             } else {
-                if (useDiff) {
-                    expect.fail('Cannot get the diff from a non-Unexpected error');
-                }
-                if (format !== 'text') {
-                    expect.fail('Cannot get the ' + format + ' representation of non-Unexpected error');
-                } else {
-                    return expect(subject.message, 'to satisfy', value);
-                }
+              expect.fail('The UnexpectedError instance does not have a diff');
+            }
+          } else {
+            subjectPen = subject.getErrorMessage({ format: format });
+          }
+          var valueType = expect.argTypes[0];
+          if (valueType.is('magicpen')) {
+            expect(subjectPen, 'to equal', value);
+          } else if (valueType.is('function') && !valueType.is('expect.it')) {
+            var expectedOutput = expect.createOutput(format);
+            var returnValue = value.call(expectedOutput, subjectPen.toString());
+            if (!expectedOutput.isEmpty()) {
+              // If the function didn't generate any expected output, assume that it ran assertions based on the serialized message
+              expect(subjectPen, 'to equal', expectedOutput);
             }
-        });
-    }
+            return returnValue;
+          } else {
+            return expect(subjectPen.toString(), 'to satisfy', value);
+          }
+        } else {
+          if (useDiff) {
+            expect.fail('Cannot get the diff from a non-Unexpected error');
+          }
+          if (format !== 'text') {
+            expect.fail(
+              'Cannot get the ' +
+                format +
+                ' representation of non-Unexpected error'
+            );
+          } else {
+            return expect(subject.message, 'to satisfy', value);
+          }
+        }
+      }
+    );
+  },
 };
diff --git a/rollup.config.js b/rollup.config.js
index 20eb0b3..1179713 100644
--- a/rollup.config.js
+++ b/rollup.config.js
@@ -3,33 +3,29 @@ const commonjs = require('rollup-plugin-commonjs');
 const resolve = require('rollup-plugin-node-resolve');
 const json = require('rollup-plugin-json');
 
-const plugins = [
-    commonjs(),
-    resolve(),
-    json()
-];
+const plugins = [commonjs(), resolve(), json()];
 
 module.exports = [
-    {
-        input: pkg.main,
-        output: {
-            file: 'unexpected-magicpen.min.js',
-            name: 'weknowhow.unexpectedMagicPen',
-            format: 'umd',
-            exports: 'named',
-            legacy: true,
-            strict: false
-        },
-        plugins
+  {
+    input: pkg.main,
+    output: {
+      file: 'unexpected-magicpen.min.js',
+      name: 'weknowhow.unexpectedMagicPen',
+      format: 'umd',
+      exports: 'named',
+      legacy: true,
+      strict: false,
+    },
+    plugins,
+  },
+  {
+    input: pkg.main,
+    output: {
+      file: 'unexpected-magicpen.esm.js',
+      format: 'esm',
+      exports: 'named',
+      strict: false,
     },
-    {
-        input: pkg.main,
-        output: {
-            file: 'unexpected-magicpen.esm.js',
-            format: 'esm',
-            exports: 'named',
-            strict: false
-        },
-        plugins
-    }
+    plugins,
+  },
 ];
diff --git a/test/unexpected-magicpen.spec.js b/test/unexpected-magicpen.spec.js
index f7d8a67..9d18690 100644
--- a/test/unexpected-magicpen.spec.js
+++ b/test/unexpected-magicpen.spec.js
@@ -1,110 +1,169 @@
 var expect = require('unexpected')
-    .clone()
-    .use(require('../lib/unexpected-magicpen'));
+  .clone()
+  .use(require('../lib/unexpected-magicpen'));
 
-expect.addAssertion('<any> to inspect as <string>', function (expect, subject, value) {
+expect
+  .addAssertion('<any> to inspect as <string>', function (
+    expect,
+    subject,
+    value
+  ) {
     expect(expect.inspect(subject).toString(), 'to equal', value);
-}).addAssertion('<any> when delayed a little bit <assertion>', function (expect, subject) {
+  })
+  .addAssertion('<any> when delayed a little bit <assertion>', function (
+    expect,
+    subject
+  ) {
     return expect.promise(function (run) {
-        setTimeout(run(function () {
-            return expect.shift();
-        }), 1);
+      setTimeout(
+        run(function () {
+          return expect.shift();
+        }),
+        1
+      );
     });
-});
+  });
 
 describe('magicpen type', function () {
-    describe('#inspect', function () {
-        it('should inspect an empty MagicPen instance', function () {
-            expect(expect.output.clone().magicPen(expect.output.clone()).toString(), 'to equal', 'magicpen()');
-        });
-
-        it('should find two pens with different formats to not to be identical', function () {
-            var MagicPen = expect.output.constructor;
-            expect(new MagicPen('text').text('foo'), 'not to equal', new MagicPen('ansi').text('foo'));
-        });
+  describe('#inspect', function () {
+    it('should inspect an empty MagicPen instance', function () {
+      expect(
+        expect.output.clone().magicPen(expect.output.clone()).toString(),
+        'to equal',
+        'magicpen()'
+      );
+    });
 
-        it('should find two format-less pens with the same contents to be identical', function () {
-            var MagicPen = expect.output.constructor;
-            expect(new MagicPen().text('foo'), 'to equal', new MagicPen().text('foo'));
-        });
+    it('should find two pens with different formats to not to be identical', function () {
+      var MagicPen = expect.output.constructor;
+      expect(
+        new MagicPen('text').text('foo'),
+        'not to equal',
+        new MagicPen('ansi').text('foo')
+      );
+    });
 
-        describe('with a pen in text format', function () {
-            var pen = expect.createOutput('text').green('abc').nl().text('def').block(function () {
-                this.text('foo').nl().text('bar');
-            });
+    it('should find two format-less pens with the same contents to be identical', function () {
+      var MagicPen = expect.output.constructor;
+      expect(
+        new MagicPen().text('foo'),
+        'to equal',
+        new MagicPen().text('foo')
+      );
+    });
 
-            it('should inspect correctly', function () {
-                expect(pen, 'to inspect as',
-                    "magicpen('text')        // abc\n" +
-                       "  .green('abc').nl()    // deffoo\n" +
-                       "  .text('def')          //    bar\n" +
-                       '  .block(function () {\n' +
-                       '    this\n' +
-                       "      .text('foo').nl()\n" +
-                       "      .text('bar');\n" +
-                       '  })'
-                );
-            });
+    describe('with a pen in text format', function () {
+      var pen = expect
+        .createOutput('text')
+        .green('abc')
+        .nl()
+        .text('def')
+        .block(function () {
+          this.text('foo').nl().text('bar');
         });
 
-        describe('with a pen in ansi format', function () {
-            var pen = expect.createOutput('ansi').green('abc').text('def').block(function () {
-                this.text('foo');
-            });
+      it('should inspect correctly', function () {
+        expect(
+          pen,
+          'to inspect as',
+          "magicpen('text')        // abc\n" +
+            "  .green('abc').nl()    // deffoo\n" +
+            "  .text('def')          //    bar\n" +
+            '  .block(function () {\n' +
+            '    this\n' +
+            "      .text('foo').nl()\n" +
+            "      .text('bar');\n" +
+            '  })'
+        );
+      });
+    });
 
-            it('should inspect correctly', function () {
-                expect(pen, 'to inspect as',
-                    "magicpen('ansi')\n" +
-                       "  .green('abc')\n" +
-                       "  .text('def')\n" +
-                       '  .block(function () {\n' +
-                       "    this.text('foo');\n" +
-                       '  })'
-                );
-            });
+    describe('with a pen in ansi format', function () {
+      var pen = expect
+        .createOutput('ansi')
+        .green('abc')
+        .text('def')
+        .block(function () {
+          this.text('foo');
         });
 
-        describe('with a pen in html format', function () {
-            var pen = expect.createOutput('html').green('abc').text('def').block(function () {
-                this.text('foo');
-            });
+      it('should inspect correctly', function () {
+        expect(
+          pen,
+          'to inspect as',
+          "magicpen('ansi')\n" +
+            "  .green('abc')\n" +
+            "  .text('def')\n" +
+            '  .block(function () {\n' +
+            "    this.text('foo');\n" +
+            '  })'
+        );
+      });
+    });
 
-            it('should inspect correctly', function () {
-                expect(pen, 'to inspect as',
-                    "magicpen('html')\n" +
-                       "  .green('abc')\n" +
-                       "  .text('def')\n" +
-                       '  .block(function () {\n' +
-                       "    this.text('foo');\n" +
-                       '  })'
-                );
-            });
+    describe('with a pen in html format', function () {
+      var pen = expect
+        .createOutput('html')
+        .green('abc')
+        .text('def')
+        .block(function () {
+          this.text('foo');
         });
+
+      it('should inspect correctly', function () {
+        expect(
+          pen,
+          'to inspect as',
+          "magicpen('html')\n" +
+            "  .green('abc')\n" +
+            "  .text('def')\n" +
+            '  .block(function () {\n' +
+            "    this.text('foo');\n" +
+            '  })'
+        );
+      });
     });
+  });
 });
 
 describe('magicPen style', function () {
-    it('renders a raw entry', function () {
-        expect(expect.createOutput('text').raw('foo'), 'to inspect as', "magicpen('text').raw('foo') // foo");
-    });
+  it('renders a raw entry', function () {
+    expect(
+      expect.createOutput('text').raw('foo'),
+      'to inspect as',
+      "magicpen('text').raw('foo') // foo"
+    );
+  });
 
-    it('renders an empty block', function () {
-        expect(
-            expect.createOutput('text').block(function () {}),
-            'to inspect as',
-            "magicpen('text').block(function () {}) // "
-        );
-    });
+  it('renders an empty block', function () {
+    expect(
+      expect.createOutput('text').block(function () {}),
+      'to inspect as',
+      "magicpen('text').block(function () {}) // "
+    );
+  });
 
-    it('renders text with an empty array of styles', function () {
-        expect(expect.createOutput('text').text('foo', []), 'to inspect as', "magicpen('text').text('foo', []) // foo");
-    });
+  it('renders text with an empty array of styles', function () {
+    expect(
+      expect.createOutput('text').text('foo', []),
+      'to inspect as',
+      "magicpen('text').text('foo', []) // foo"
+    );
+  });
 
-    it('renders text with a single style not defined as a top-level style', function () {
-        expect(expect.createOutput('text').text('foo', ['blabla']), 'to inspect as', "magicpen('text').text('foo', [ 'blabla' ]) // foo");
-    });
+  it('renders text with a single style not defined as a top-level style', function () {
+    expect(
+      expect.createOutput('text').text('foo', ['blabla']),
+      'to inspect as',
+      "magicpen('text').text('foo', [ 'blabla' ]) // foo"
+    );
+  });
 
-    it('renders text with several styles', function () {
-        expect(expect.createOutput('text').text('foo', ['quux', 'baz']), 'to inspect as', "magicpen('text').text('foo', [ 'quux', 'baz' ]) // foo");
-    });
+  it('renders text with several styles', function () {
+    expect(
+      expect.createOutput('text').text('foo', ['quux', 'baz']),
+      'to inspect as',
+      "magicpen('text').text('foo', [ 'quux', 'baz' ]) // foo"
+    );
+  });
 });