diff --git a/scripts/dev/check_coverage.py b/scripts/dev/check_coverage.py
index 8d6f3ccae..5c678ac96 100644
--- a/scripts/dev/check_coverage.py
+++ b/scripts/dev/check_coverage.py
@@ -64,6 +64,8 @@ PERFECT_FILES = [
      'browser/webkit/cookies.py'),
     ('tests/unit/browser/test_history.py',
      'browser/history.py'),
+    ('tests/unit/browser/test_pdfjs.py',
+     'browser/pdfjs.py'),
     ('tests/unit/browser/webkit/http/test_http.py',
      'browser/webkit/http.py'),
     ('tests/unit/browser/webkit/http/test_content_disposition.py',
diff --git a/tests/unit/browser/test_pdfjs.py b/tests/unit/browser/test_pdfjs.py
index c30d9fb08..02306c0ad 100644
--- a/tests/unit/browser/test_pdfjs.py
+++ b/tests/unit/browser/test_pdfjs.py
@@ -21,6 +21,18 @@ import pytest
 from PyQt5.QtCore import QUrl
 
 from qutebrowser.browser import pdfjs
+from qutebrowser.utils import usertypes
+
+
+@pytest.mark.parametrize('available, snippet', [
+    (True, '<title>PDF.js viewer</title>'),
+    (False, '<h1>No pdf.js installation found</h1>'),
+])
+def test_generate_pdfjs_page(available, snippet, monkeypatch):
+    monkeypatch.setattr(pdfjs, 'is_available', lambda: available)
+    content = pdfjs.generate_pdfjs_page(QUrl('https://example.com/'))
+    print(content)
+    assert snippet in content
 
 
 # Note that we got double protection, once because we use QUrl.FullyEncoded and
@@ -41,6 +53,60 @@ def test_generate_pdfjs_script(url, expected):
     assert 'PDFView' in actual
 
 
+@pytest.mark.parametrize('new_qt, backend, expected', [
+    (True, usertypes.Backend.QtWebEngine, False),
+    (True, usertypes.Backend.QtWebKit, False),
+    (False, usertypes.Backend.QtWebEngine, True),
+    (False, usertypes.Backend.QtWebKit, False),
+])
+def test_generate_pdfjs_script_disable_object_url(monkeypatch,
+                                                  new_qt, backend, expected):
+    monkeypatch.setattr(pdfjs.qtutils, 'version_check', lambda _v: new_qt)
+    monkeypatch.setattr(pdfjs.objects, 'backend', backend)
+
+    script = pdfjs._generate_pdfjs_script(QUrl('https://example.com/'))
+    assert ('PDFJS.disableCreateObjectURL' in script) == expected
+
+
+class TestResources:
+
+    @pytest.fixture
+    def read_system_mock(self, mocker):
+        return mocker.patch.object(pdfjs, '_read_from_system', autospec=True)
+
+    @pytest.fixture
+    def read_file_mock(self, mocker):
+        return mocker.patch.object(pdfjs.utils, 'read_file', autospec=True)
+
+    def test_get_pdfjs_res_system(self, read_system_mock):
+        read_system_mock.return_value = (b'content', 'path')
+
+        assert pdfjs.get_pdfjs_res_and_path('web/test') == (b'content', 'path')
+        assert pdfjs.get_pdfjs_res('web/test') == b'content'
+
+        read_system_mock.assert_called_with('/usr/share/pdf.js/',
+                                            ['web/test', 'test'])
+
+    def test_get_pdfjs_res_bundled(self, read_system_mock, read_file_mock):
+        read_system_mock.return_value = (None, None)
+
+        read_file_mock.return_value = b'content'
+
+        assert pdfjs.get_pdfjs_res_and_path('web/test') == (b'content', None)
+        assert pdfjs.get_pdfjs_res('web/test') == b'content'
+
+        for path in pdfjs.SYSTEM_PDFJS_PATHS:
+            read_system_mock.assert_any_call(path, ['web/test', 'test'])
+
+    def test_get_pdfjs_res_not_found(self, read_system_mock, read_file_mock):
+        read_system_mock.return_value = (None, None)
+        read_file_mock.side_effect = FileNotFoundError
+
+        with pytest.raises(pdfjs.PDFJSNotFound,
+                           match="Path 'web/test' not found"):
+            pdfjs.get_pdfjs_res_and_path('web/test')
+
+
 @pytest.mark.parametrize('path, expected', [
     ('web/viewer.js', 'viewer.js'),
     ('build/locale/foo.bar', 'locale/foo.bar'),
@@ -49,3 +115,53 @@ def test_generate_pdfjs_script(url, expected):
 ])
 def test_remove_prefix(path, expected):
     assert pdfjs._remove_prefix(path) == expected
+
+
+@pytest.mark.parametrize('names, expected_name', [
+    (['one'], 'one'),
+    (['doesnotexist', 'two'], 'two'),
+    (['one', 'two'], 'one'),
+    (['does', 'not', 'onexist'], None),
+])
+def test_read_from_system(names, expected_name, tmpdir):
+    file1 = tmpdir / 'one'
+    file1.write_text('text1', encoding='ascii')
+    file2 = tmpdir / 'two'
+    file2.write_text('text2', encoding='ascii')
+
+    if expected_name == 'one':
+        expected = (b'text1', str(file1))
+    elif expected_name == 'two':
+        expected = (b'text2', str(file2))
+    elif expected_name is None:
+        expected = (None, None)
+
+    assert pdfjs._read_from_system(str(tmpdir), names) == expected
+
+
+@pytest.mark.parametrize('available', [True, False])
+def test_is_available(available, mocker):
+    mock = mocker.patch.object(pdfjs, 'get_pdfjs_res', autospec=True)
+    if available:
+        mock.return_value = b'foo'
+    else:
+        mock.side_effect = pdfjs.PDFJSNotFound('build/pdf.js')
+
+    assert pdfjs.is_available() == available
+
+
+@pytest.mark.parametrize('mimetype, enabled, expected', [
+    ('application/pdf', True, True),
+    ('application/x-pdf', True, True),
+    ('application/octet-stream', True, False),
+    ('application/pdf', False, False),
+])
+def test_should_use_pdfjs(mimetype, enabled, expected, config_stub):
+    config_stub.val.content.pdfjs = enabled
+    assert pdfjs.should_use_pdfjs(mimetype) == expected
+
+
+def test_get_main_url():
+    expected = ('qute://pdfjs/web/viewer.html?file='
+                'qute://pdfjs/file?filename%3Dhello?world.pdf')
+    assert pdfjs.get_main_url('hello?world.pdf') == QUrl(expected)