diff --git a/benchmark/TensorAlgebraBenchmarks/TensorAlgebraBenchmarks.jl b/benchmark/TensorAlgebraBenchmarks/TensorAlgebraBenchmarks.jl
index 66342fc..7693540 100644
--- a/benchmark/TensorAlgebraBenchmarks/TensorAlgebraBenchmarks.jl
+++ b/benchmark/TensorAlgebraBenchmarks/TensorAlgebraBenchmarks.jl
@@ -42,5 +42,10 @@ function _δδ_λ_2D(λ::Float64)
     λ)
 end
 
+A = TensorValue(1.:9...)
+A = A + A' + I3
+
 SUITE["Tensor algebra"]["δδ_μ_2d"] = @benchmarkable δᵢₖδⱼₗ2D + δᵢₗδⱼₖ2D
 SUITE["Tensor algebra"]["δδ_λ_2d"] = @benchmarkable 1.0 * δᵢⱼδₖₗ2D
+SUITE["Tensor algebra"]["Cofactor"] = cof(A)
+SUITE["Tensor algebra"]["Det(A)Inv(A')"] = det(A)*inv(A')
diff --git a/src/TensorAlgebra/Functions.jl b/src/TensorAlgebra/Functions.jl
index 782e8cd..3cdf3bf 100644
--- a/src/TensorAlgebra/Functions.jl
+++ b/src/TensorAlgebra/Functions.jl
@@ -17,7 +17,7 @@ end
 Calculate the cofactor of a matrix.
 """
 function cof(A::TensorValue)
-  return det(A)*inv(A')
+  0.5A×A
 end
 
 
diff --git a/test/TestTensorAlgebra/TensorAlgebra.jl b/test/TestTensorAlgebra/TensorAlgebraTests.jl
similarity index 95%
rename from test/TestTensorAlgebra/TensorAlgebra.jl
rename to test/TestTensorAlgebra/TensorAlgebraTests.jl
index 126ecfc..c84ecff 100644
--- a/test/TestTensorAlgebra/TensorAlgebra.jl
+++ b/test/TestTensorAlgebra/TensorAlgebraTests.jl
@@ -104,5 +104,13 @@ end
 @testset "sqrt" begin
   A = TensorValue(1.:9...)
   A = A'*A + I3
-  @test isapprox(sqrt(A), TensorValue(sqrt(get_array(A))), rtol=1e-14)
+  sqrtA = TensorValue(sqrt(get_array(A)))
+  @test isapprox(sqrt(A), sqrtA, rtol=1e-14)
+end
+
+
+@testset "cofactor" begin
+  A = TensorValue(1.:9...) + I3
+  cofA = det(A) * inv(A')
+  @test isapprox(cof(A), cofA)
 end
diff --git a/test/TestTensorAlgebra/runtests.jl b/test/TestTensorAlgebra/runtests.jl
index 7b354b0..7f3e541 100644
--- a/test/TestTensorAlgebra/runtests.jl
+++ b/test/TestTensorAlgebra/runtests.jl
@@ -1,7 +1,11 @@
+using HyperFEM
+using Gridap
+using Test
+
 @testset "TensorAlgebra" begin
 
-    @time begin
-        include("TensorAlgebra.jl")
-    end
+  @time begin
+    include("TensorAlgebraTests.jl")
+  end
 
-end
\ No newline at end of file
+end