Exit with non-0 return code if no tests were run

A new flag, `--allow-running-no-tests` was added to override this
behaviour if exit code of 0 was desired.

This change also made `-w NoTests` obsolete, and so it has been
removed.

tests/ExtraTests/CMakeLists.txt

@@ -299,6 +299,22 @@ set_tests_properties(
 #    PASS_REGULAR_EXPRESSION "Pretty please, break into debugger"
 #)
 
+add_executable(NoTests ${TESTS_DIR}/X92-NoTests.cpp)
+target_link_libraries(NoTests PRIVATE Catch2::Catch2WithMain)
+
+add_test(
+  NAME TestSpecs::EmptySpecWithNoTestsFails
+  COMMAND $<TARGET_FILE:NoTests>
+)
+set_tests_properties(TestSpecs::EmptySpecWithNoTestsFails
+  PROPERTIES
+    WILL_FAIL ON
+)
+add_test(
+  NAME TestSpecs::OverrideFailureWithEmptySpec
+  COMMAND $<TARGET_FILE:NoTests> --allow-running-no-tests
+)
+
 set( EXTRA_TEST_BINARIES
     PrefixedMacros
     DisabledMacros
@@ -310,6 +326,7 @@ set( EXTRA_TEST_BINARIES
     DuplicatedTestCases-SameNameAndTags
     DuplicatedTestCases-SameNameDifferentTags
     DuplicatedTestCases-DuplicatedTestCaseMethods
+    NoTests
 #    DebugBreakMacros
 )
 

tests/ExtraTests/X92-NoTests.cpp

@@ -0,0 +1,11 @@
+
+//              Copyright Catch2 Authors
+// Distributed under the Boost Software License, Version 1.0.
+//   (See accompanying file LICENSE_1_0.txt or copy at
+//        https://www.boost.org/LICENSE_1_0.txt)
+
+// SPDX-License-Identifier: BSL-1.0
+
+/**\file
+ * Links into executable with no tests which should fail when run
+ */