Initial commit for integration tests. Experimental. Playing with potential syntax

test/integration/tests/simple.rb

@@ -0,0 +1,7 @@
+add_test('basic') { |prj|
+  prj.set_body <<~CMAKE
+    CPMAddPackage("gh:cpm-cmake/testpack-adder")
+    add_executable(using-adder using-adder.cpp)
+    target_link_libraries(using-adder PRIVATE adder)
+  CMAKE
+}