add test with zero axis

Author: ogauthe

test/test_factorizations.jl

@@ -147,6 +147,20 @@ end
   @test A ≈ A′
   @test size(U, 1) * size(U, 2) == size(U, 3) # U is unitary
   @test size(Vᴴ, 1) == size(Vᴴ, 2) * size(Vᴴ, 3) # V is unitary
+
+  U, S, Vᴴ = @constinferred svd(A, labels_A, labels_A, (); full=true)
+  @test A == Acopy # should not have altered initial array
+  US, labels_US = contract(U, (labels_A..., :u), S, (:u, :v))
+  A′ = contract(labels_A, US, labels_US, Vᴴ, (:v,))
+  @test A ≈ A′
+  @test size(Vᴴ, 1) == 1
+
+  U, S, Vᴴ = @constinferred svd(A, labels_A, (), labels_A; full=true)
+  @test A == Acopy # should not have altered initial array
+  US, labels_US = contract(U, (:u,), S, (:u, :v))
+  A′ = contract(labels_A, US, labels_US, Vᴴ, (:v, labels_A...))
+  @test A ≈ A′
+  @test size(U, 2) == 1
 end
 
 @testset "Compact SVD ($T)" for T in elts
@@ -166,6 +180,20 @@ end
 
   Svals = @constinferred svdvals(A, labels_A, labels_U, labels_Vᴴ)
   @test Svals ≈ diag(S)
+
+  U, S, Vᴴ = @constinferred svd(A, labels_A, labels_A, (); full=false)
+  @test A == Acopy # should not have altered initial array
+  US, labels_US = contract(U, (labels_A..., :u), S, (:u, :v))
+  A′ = contract(labels_A, US, labels_US, Vᴴ, (:v,))
+  @test A ≈ A′
+  @test size(U, ndims(U)) == 1 == size(Vᴴ, 1)
+
+  U, S, Vᴴ = @constinferred svd(A, labels_A, (), labels_A; full=false)
+  @test A == Acopy # should not have altered initial array
+  US, labels_US = contract(U, (:u,), S, (:u, :v))
+  A′ = contract(labels_A, US, labels_US, Vᴴ, (:v, labels_A...))
+  @test A ≈ A′
+  @test size(U, 1) == 1 == size(Vᴴ, 1)
 end
 
 @testset "Truncated SVD ($T)" for T in elts