diff --git a/tests/base.py b/tests/base.py
index 892159d..2ad6351 100644
--- a/tests/base.py
+++ b/tests/base.py
@@ -18,7 +18,6 @@ class BaseTestClass:
 
     @classmethod
     def setup_class(cls):
-        cls.mode = "mupdf"
         cls.cams_file_name = os.getenv("CAMS_CAS_FILE")
         cls.new_cams_file_name = os.getenv("CAMS_CAS_FILE_NEW")
         cls.cams_summary_file_name = os.getenv("CAMS_CAS_SUMMARY")
@@ -37,8 +36,7 @@ def setup_class(cls):
         ]
 
     def read_pdf(self, filename, password, output="dict"):
-        use_pdfminer = self.mode == "pdfminer"
-        return read_cas_pdf(filename, password, output=output, force_pdfminer=use_pdfminer)
+        return read_cas_pdf(filename, password, output=output)
 
     def test_output_json(self):
         for filename, password, num_folios, _ in self.pdf_files:
@@ -81,8 +79,6 @@ def test_read_dict(self):
 
         for pdf_file, pdf_password, _, num_schemes in self.pdf_files:
             args = [pdf_file, "-p", pdf_password, "-a"]
-            if self.mode != "mupdf":
-                args.append("--force-pdfminer")
             result = runner.invoke(cli, args)
             assert result.exit_code == 0
             clean_output = self.ansi_cleaner.sub("", result.output)
diff --git a/tests/test_pdfminer.py b/tests/test_pdfminer.py
index 6b8c3e0..c4a6b9b 100644
--- a/tests/test_pdfminer.py
+++ b/tests/test_pdfminer.py
@@ -1,18 +1,50 @@
+import sys
+
 import pytest
 from pdfminer.layout import LTTextBoxHorizontal
 
+from casparser import read_cas_pdf
 from casparser.exceptions import CASParseError
 
 from .base import BaseTestClass
 
+try:
+    import builtins
+except ImportError:
+    import __builtin__ as builtins
+
+realimport = builtins.__import__
+
+
+def mockimport(name, *args):
+    """Force ImportError on fitz and/or mupdf import and make casparser fallback to pdfminer"""
+    if name in ("fitz", "mupdf"):
+        raise ImportError
+    return realimport(name, *args)
+
+
+@pytest.fixture(scope="class")
+def monkeyclass():
+    with pytest.MonkeyPatch.context() as mp:
+        yield mp
 
+
+@pytest.fixture(scope="class")
+def use_pdfminer(monkeyclass):
+    if "fitz" in sys.modules:
+        del sys.modules["fitz"]
+    monkeyclass.setattr(builtins, "__import__", mockimport)
+    yield
+    monkeyclass.setattr(builtins, "__import__", realimport)
+
+
+@pytest.mark.usefixtures("use_pdfminer")
 class TestPDFMiner(BaseTestClass):
     """Test pdfminer parser."""
 
     @classmethod
     def setup_class(cls):
         BaseTestClass.setup_class()
-        cls.mode = "pdfminer"
 
     def test_bad_investor_info(self):
         from casparser.parsers.pdfminer import parse_investor_info
@@ -22,3 +54,8 @@ def test_bad_investor_info(self):
             box.get_text()
             parse_investor_info([], 0, 0)
         assert "Unable to parse investor data" in str(exc_info)
+
+    def test_invalid_file_type(self):
+        with pytest.raises(CASParseError) as exc_info:
+            read_cas_pdf(1, "", force_pdfminer=True)
+        assert "Invalid input" in str(exc_info)