diff --git a/Makefile b/Makefile
index 0888ae3b53c..f2e81b0c725 100644
--- a/Makefile
+++ b/Makefile
@@ -916,8 +916,8 @@ ystests: $(TARGETS) $(EXTRA_TARGETS)
 
 # Unit test
 unit-test: libyosys.so
-	@$(MAKE) -C $(UNITESTPATH) CXX="$(CXX)" CPPFLAGS="$(CPPFLAGS)" \
-		CXXFLAGS="$(CXXFLAGS)" LIBS="$(LIBS)" ROOTPATH="$(CURDIR)"
+	@$(MAKE) -C $(UNITESTPATH) CXX="$(CXX)" CC="$(CC)" CPPFLAGS="$(CPPFLAGS)" \
+		CXXFLAGS="$(CXXFLAGS)" LINKFLAGS="$(LINKFLAGS)" LIBS="$(LIBS)" ROOTPATH="$(CURDIR)"
 
 clean-unit-test:
 	@$(MAKE) -C $(UNITESTPATH) clean
diff --git a/kernel/rtlil.h b/kernel/rtlil.h
index da57e01519b..783dcb4dd82 100644
--- a/kernel/rtlil.h
+++ b/kernel/rtlil.h
@@ -667,6 +667,8 @@ struct RTLIL::Const
 {
 	short flags;
 private:
+	friend class KernelRtlilTest;
+	FRIEND_TEST(KernelRtlilTest, ConstStr);
 	using bitvectype = std::vector<RTLIL::State>;
 	enum class backing_tag: bool { bits, string };
 	// Do not access the union or tag even in Const methods unless necessary
diff --git a/kernel/yosys_common.h b/kernel/yosys_common.h
index 56d2356b102..cd5d7e92d44 100644
--- a/kernel/yosys_common.h
+++ b/kernel/yosys_common.h
@@ -50,6 +50,8 @@
 #include <sys/stat.h>
 #include <errno.h>
 
+#include <gtest/gtest_prod.h>
+
 #ifdef WITH_PYTHON
 #include <Python.h>
 #endif
diff --git a/tests/unit/Makefile b/tests/unit/Makefile
index b4a752f8f47..4c2848ea28f 100644
--- a/tests/unit/Makefile
+++ b/tests/unit/Makefile
@@ -15,7 +15,7 @@ TESTS := $(addprefix $(BINTEST)/, $(basename $(ALLTESTFILE:%Test.cc=%Test.o)))
 all: prepare $(TESTS) run-tests
 
 $(BINTEST)/%: $(OBJTEST)/%.o
-	$(CXX) -L$(ROOTPATH) $(RPATH)=$(ROOTPATH) -o $@ $^ $(LIBS) \
+	$(CXX) -L$(ROOTPATH) $(RPATH)=$(ROOTPATH) $(LINKFLAGS) -o $@ $^ $(LIBS) \
 		$(GTESTFLAG) $(EXTRAFLAGS)
 
 $(OBJTEST)/%.o: $(basename $(subst $(OBJTEST),.,%)).cc
diff --git a/tests/unit/kernel/rtlilTest.cc b/tests/unit/kernel/rtlilTest.cc
index d9eeed555ad..1d5ef3a833c 100644
--- a/tests/unit/kernel/rtlilTest.cc
+++ b/tests/unit/kernel/rtlilTest.cc
@@ -1,14 +1,79 @@
 #include <gtest/gtest.h>
-
-#include "kernel/yosys.h"
 #include "kernel/rtlil.h"
 
 YOSYS_NAMESPACE_BEGIN
 
-TEST(KernelRtlilTest, getReferenceValid)
-{
-	//TODO: Implement rtlil test
-	EXPECT_EQ(33, 33);
+namespace RTLIL {
+
+	class KernelRtlilTest : public testing::Test {};
+
+	TEST_F(KernelRtlilTest, ConstAssignCompare)
+	{
+		Const c1;
+		Const c2;
+		c2 = c1;
+		Const c3(c2);
+		EXPECT_TRUE(c2 == c3);
+		EXPECT_FALSE(c2 < c3);
+	}
+
+	TEST_F(KernelRtlilTest, ConstStr) {
+		// We have multiple distinct sections since it's annoying
+		// to list multiple testcases as friends of Const in kernel/rtlil.h
+		{
+			std::string foo = "foo";
+			Const c1 = foo;
+			Const c2;
+			c2 = c1;
+			Const c3(c2);
+			EXPECT_TRUE(c1.is_str());
+			EXPECT_TRUE(c2.is_str());
+			EXPECT_TRUE(c3.is_str());
+		}
+
+		{
+			// A binary constant is bitvec backed
+			Const cb1(0, 10);
+			Const cb2(1, 10);
+			Const cb3(cb2);
+			std::vector<bool> v1 {false, true};
+			std::vector<State> v2 {State::S0, State::S1};
+			Const cb4(v1);
+			Const cb5(v2);
+			EXPECT_TRUE(cb4 == cb5);
+			EXPECT_TRUE(cb1.is_bits());
+			EXPECT_TRUE(cb2.is_bits());
+			EXPECT_TRUE(cb3.is_bits());
+			EXPECT_TRUE(cb4.is_bits());
+			EXPECT_TRUE(cb5.is_bits());
+			EXPECT_EQ(cb1.size(), 10);
+			EXPECT_EQ(cb2.size(), 10);
+			EXPECT_EQ(cb3.size(), 10);
+		}
+
+		{
+			// A string constructed Const starts off packed
+			std::string foo = "foo";
+			Const cs1 = foo;
+			EXPECT_TRUE(cs1.is_str());
+
+			// It can be iterated without mutating
+			int i = 0;
+			for (auto bit : cs1) {
+				i += bit;
+			}
+			EXPECT_EQ(i, 16);
+			EXPECT_TRUE(cs1.is_str());
+
+			// It can be mutated with the bits() view
+			// and decays into unpacked
+			for (auto& bit : cs1.bits()) {
+				bit = State::Sx;
+			}
+			EXPECT_TRUE(cs1.is_bits());
+		}
+
+	}
 }
 
 YOSYS_NAMESPACE_END