Small source_cache test

test/integration/test_a_lib.rb

@@ -0,0 +1,20 @@
+require_relative './lib'
+
+# Tests and experiments with the integration test framework itself
+
+class ALib < IntegrationTest
+  def test_zza
+    f = -> {
+      assert_equal 2, 2
+    }
+    f.()
+  end
+
+  def test_b
+    test_foo('xxx')
+  end
+
+  def test_foo(xxx)
+    assert_equal 'xxx', xxx
+  end
+end