diff --git a/.gitmodules b/.gitmodules
deleted file mode 100644
index 6051b7f2..00000000
--- a/.gitmodules
+++ /dev/null
@@ -1,3 +0,0 @@
-[submodule "extern/googletest"]
-	path = extern/googletest
-	url = ../../google/googletest.git
diff --git a/CPPLINT.cfg b/CPPLINT.cfg
index d497667b..0a1758da 100644
--- a/CPPLINT.cfg
+++ b/CPPLINT.cfg
@@ -5,6 +5,8 @@ linelength=120  # As in .clang-format
 filter=-build/c++11  # Reports e.g. chrono and thread, which overlap with Chromium's API. Not applicable to general C++ projects.
 filter=-build/include_order  # Requires unusual include order that encourages creating not self-contained headers
 filter=-readability/nolint  # Conflicts with clang-tidy
+filter=-readability/check  # Catch uses CHECK(a == b) (Tests only)
+filter=-build/namespaces  # Currently using it for one test (Tests only)
 filter=-runtime/references  # Requires fundamental change of API, don't see need for this
 filter=-whitespace/blank_line  # Unnecessarily strict with blank lines that otherwise help with readability
 filter=-whitespace/indent  # Requires strange 3-space indent of private/protected/public markers
diff --git a/extern/googletest b/extern/googletest
deleted file mode 160000
index 859bfe89..00000000
--- a/extern/googletest
+++ /dev/null
@@ -1 +0,0 @@
-Subproject commit 859bfe8981d6724c4ea06e73d29accd8588f3230
diff --git a/tests/HelpersTest.cpp b/tests/HelpersTest.cpp
index ae1d009d..0c032fbc 100644
--- a/tests/HelpersTest.cpp
+++ b/tests/HelpersTest.cpp
@@ -1002,11 +1002,11 @@ TEST_CASE("Types: TypeName", "[helpers]") {
 
 TEST_CASE("Types: OverflowSmall", "[helpers]") {
     signed char x;
-    auto strmax = std::to_string(SCHAR_MAX + 1);
+    auto strmax = std::to_string(std::numeric_limits<signed char>::max() + 1);
     CHECK_FALSE(CLI::detail::lexical_cast(strmax, x));
 
     unsigned char y;
-    strmax = std::to_string(UINT8_MAX + 1);
+    strmax = std::to_string(std::numeric_limits<unsigned char>::max() + 1);
     CHECK_FALSE(CLI::detail::lexical_cast(strmax, y));
 }
 
@@ -1024,7 +1024,7 @@ TEST_CASE("Types: LexicalCastInt", "[helpers]") {
     CHECK_FALSE(CLI::detail::lexical_cast(signed_input, x_unsigned));
 
     unsigned char y;
-    std::string overflow_input = std::to_string(UINT64_MAX) + "0";
+    std::string overflow_input = std::to_string(std::numeric_limits<uint64_t>::max()) + "0";
     CHECK_FALSE(CLI::detail::lexical_cast(overflow_input, y));
 
     char y_signed;
diff --git a/tests/main.cpp b/tests/main.cpp
index 0c7c351f..f1c2725f 100644
--- a/tests/main.cpp
+++ b/tests/main.cpp
@@ -1,2 +1,8 @@
+// Copyright (c) 2017-2020, University of Cincinnati, developed by Henry Schreiner
+// under NSF AWARD 1414736 and by the respective contributors.
+// All rights reserved.
+//
+// SPDX-License-Identifier: BSD-3-Clause
+
 #define CATCH_CONFIG_MAIN
 #include "catch.hpp"