Migrate from Catch to Doctest

This reduces the build times of the test suite by about two thirds in my
testing in another project.

Change-Id: I8a5da3aff0956796c718d13237d0620f48316029
Depends-on: https://gerrit.cesnet.cz/c/CzechLight/dependencies/+/1580
diff --git a/tests/doctest_integration.cpp b/tests/doctest_integration.cpp
new file mode 100644
index 0000000..b333b7d
--- /dev/null
+++ b/tests/doctest_integration.cpp
@@ -0,0 +1,24 @@
+#define DOCTEST_CONFIG_IMPLEMENT_WITH_MAIN
+#include <doctest/doctest.h>
+#include <trompeloeil.hpp>
+
+namespace trompeloeil
+{
+  template <>
+  void reporter<specialized>::send(
+    severity s,
+    const char* file,
+    unsigned long line,
+    const char* msg)
+  {
+    auto f = line ? file : "[file/line unavailable]";
+    if (s == severity::fatal)
+    {
+      ADD_FAIL_AT(f, line, msg);
+    }
+    else
+    {
+      ADD_FAIL_CHECK_AT(f, line, msg);
+    }
+  }
+}