Fix equality test for expected<void,E>

tests/relops.cpp

@@ -2,5 +2,16 @@
 #include <tl/expected.hpp>
 
 TEST_CASE("Relational operators", "[relops]") {
-    //TODO
+  tl::expected<int, int> o1 = 42;
+  tl::expected<int, int> o2{tl::unexpect, 0};
+  const tl::expected<int, int> o3 = 42;
+
+  REQUIRE(o1 == o1);
+  REQUIRE(o1 != o2);
+  REQUIRE(o1 == o3);
+  REQUIRE(o3 == o3);
+
+  tl::expected<void, int> o6;
+
+  REQUIRE(o6 == o6);
 }