diff --git a/test/constratint_matrices.jl b/test/constratint_matrices.jl
new file mode 100644
index 0000000..afdee61
--- /dev/null
+++ b/test/constratint_matrices.jl
@@ -0,0 +1,21 @@
+@testset "ConstraintMatrix" begin
+    @test PropertyT.ConstraintMatrix{Float64}([-1, 2, -1, 1, 4, 2, 6], 3, 2, π) isa AbstractMatrix
+
+    cm = PropertyT.ConstraintMatrix{Float64}([-1, 2, -1, 1, 4, 2, 6], 3, 2, π)
+
+    @test cm == Float64[
+        -π π
+        2π 0.0
+        0.0 π
+    ]
+
+    @test collect(PropertyT.nzpairs(cm)) == [
+        1 => 3.141592653589793
+        2 => 3.141592653589793
+        2 => 3.141592653589793
+        4 => 3.141592653589793
+        6 => 3.141592653589793
+        1 => -3.141592653589793
+        1 => -3.141592653589793
+    ]
+end
diff --git a/test/runtests.jl b/test/runtests.jl
index daf0aa3..cdeac69 100644
--- a/test/runtests.jl
+++ b/test/runtests.jl
@@ -17,6 +17,7 @@ include("optimizers.jl")
 
 @testset "PropertyT" begin
 
+    include("constratint_matrices.jl")
     include("actions.jl")
 
     include("1703.09680.jl")