Add tests and fix README

Author: YingboMa

Project.toml

@@ -15,9 +15,10 @@ julia = "1.2"
 BandedMatrices = "aae01518-5342-5314-be14-df237901396f"
 BlockBandedMatrices = "ffab5731-97b5-5995-9138-79e8c1846df0"
 LabelledArrays = "2ee39098-c373-598a-b85f-a56591580800"
+Random = "9a3f8284-a2c9-5f02-9a11-845980a1fd5c"
 StaticArrays = "90137ffa-7385-5640-81b9-e52037218182"
 SuiteSparse = "4607b0f0-06f3-5cda-b6b1-a6196a1729e9"
 Test = "8dfed614-e22c-5e08-85e1-65c5234f0b40"
 
 [targets]
-test = ["Test", "LabelledArrays", "StaticArrays", "BandedMatrices", "BlockBandedMatrices", "SuiteSparse"]
+test = ["Test", "LabelledArrays", "StaticArrays", "BandedMatrices", "BlockBandedMatrices", "SuiteSparse", "Random"]

README.md

@@ -67,8 +67,9 @@ cheaply.
 
 ## issingular(A)
 
-Return an instance of the LU factorization object with the correct type
-cheaply.
+Check singularity by factorization or checking zeros of structured matrices.
+
+*Warning*: `rank` is a better choice for some matrices.
 
 ## List of things to add
 

test/runtests.jl

@@ -141,3 +141,21 @@ using SuiteSparse
   end
   @test lu_instance(1) === 1
 end
+
+using Random
+using ArrayInterface: issingular
+@testset "issingular" begin
+    for T in [Float64, ComplexF64]
+        R = randn(MersenneTwister(2), T, 5, 5)
+        S = Symmetric(R)
+        L = UpperTriangular(R)
+        U = LowerTriangular(R)
+        @test all(!issingular, [R, S, L, U])
+        R[:, 2] .= 0
+        @test all(issingular, [R, L, U])
+        @test !issingular(S)
+        R[2, :] .= 0
+        @test issingular(S)
+        @test all(!issingular, [UnitLowerTriangular(R), UnitUpperTriangular(R)])
+    end
+end