Add tests

Author: lkdvos

test/basics/test_diagonal.jl

@@ -0,0 +1,25 @@
+using LinearAlgebra: Diagonal, diagind
+using SparseArraysBase:
+  eachstoredindex,
+  getstoredindex,
+  getunstoredindex,
+  setstoredindex!,
+  isstored,
+  storedlength,
+  storedpairs,
+  storedvalues
+
+using Test: @test, @testset
+
+elts = (Float32, Float64, Complex{Float32}, Complex{Float64})
+
+@testset "Diagonal{$T}" for T in elts
+  L = 4
+  D = Diagonal(rand(T, 4))
+  @test storedlength(D) == 4
+  @test eachstoredindex(D) == diagind(D, IndexCartesian())
+  @test isstored(D, 2, 2)
+  @test getstoredindex(D, 2, 2) == D[2, 2]
+  @test !isstored(D, 2, 1)
+  @test getunstoredindex(D, 2, 2) == zero(T)
+end