diff --git a/tests/coverage.h b/tests/coverage.h
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+/*
+ * Copyright (c) 2017, Patrick Pelissier
+ * All rights reserved.
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are met:
+ * + Redistributions of source code must retain the above copyright
+ *   notice, this list of conditions and the following disclaimer.
+ * + Redistributions in binary form must reproduce the above copyright
+ *   notice, this list of conditions and the following disclaimer in the
+ *   documentation and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND ANY
+ * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
+ * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+ * DISCLAIMED. IN NO EVENT SHALL THE REGENTS AND CONTRIBUTORS BE LIABLE FOR ANY
+ * DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
+ * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
+ * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
+ * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
+ * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+*/
+
+/* Coverage helper header.
+   Computing coverage for a generic macro expansing library is not trivial
+   as there is no tool to do it normally.
+
+   That's why a special way has been designed:
+   *) Put the code to coverage within the macros START_COVERAGE & END_COVERAGE
+   (without forgetting to include the header coverage.h before)
+   #include "coverage.h"
+   START_COVERAGE
+   [code to be expanded & to be coveraged]
+   END_COVERAGE
+
+   Run the coverage in the makefile like this:
+   *) make coverage-test/test-marray.c
+   
+   View the coverage file test-marray.c.gcov
+   It'll contain the macro expanded & annotated.
+*/
+   
+#ifdef WITHIN_COVERAGE
+/* For coverage build, do not expand the
+   typical macros assert, NULL, etc. */
+#undef assert
+#undef NULL
+#undef M_LIKELY
+#undef M_UNLIKELY
+#else
+/* For normal builds, empty macros which does nothing */
+#define START_COVERAGE
+#define END_COVERAGE
+#endif