added tests escape html function

tests/lib/escapeHtmlCharacters-test.js

@@ -0,0 +1,48 @@
+const { escapeHtmlCharacters } = require('browser/lib/utils')
+const test = require('ava')
+
+test('escapeHtmlCharacters should return the original string if nothing needed to escape', t => {
+  const input = 'Nothing to be escaped'
+  const expected = 'Nothing to be escaped'
+  const actual = escapeHtmlCharacters(input)
+  t.is(actual, expected)
+})
+
+test('escapeHtmlCharacters should skip code block if that option is enabled', t => {
+  const input = `    <no escape>
+<escapeMe>`
+  const expected = `    <no escape>
+&lt;escapeMe&gt;`
+  const actual = escapeHtmlCharacters(input, { detectCodeBlock: true })
+  t.is(actual, expected)
+})
+
+test('escapeHtmlCharacters should NOT skip character not in code block but start with 4 spaces', t => {
+  const input = '4 spaces    &'
+  const expected = '4 spaces    &amp;'
+  const actual = escapeHtmlCharacters(input, { detectCodeBlock: true })
+  t.is(actual, expected)
+})
+
+test('escapeHtmlCharacters should NOT skip code block if that option is NOT enabled', t => {
+  const input = `    <no escape>
+<escapeMe>`
+  const expected = `    &lt;no escape&gt;
+&lt;escapeMe&gt;`
+  const actual = escapeHtmlCharacters(input)
+  t.is(actual, expected)
+})
+
+test('escapeHtmlCharacters should NOT escape & character if it\'s a part of an escaped character', t => {
+  const input = 'Do not escape &amp; or &quot; but do escape &'
+  const expected = 'Do not escape &amp; or &quot; but do escape &amp;'
+  const actual = escapeHtmlCharacters(input)
+  t.is(actual, expected)
+})
+
+test('escapeHtmlCharacters should return the correct result', t => {
+  const input = '& < > " \''
+  const expected = '&amp; &lt; &gt; &quot; &#39;'
+  const actual = escapeHtmlCharacters(input)
+  t.is(actual, expected)
+})