test addition of (symmetric) tridiagonal matrices and I; closes Julia…

…Lang#28994 (JuliaLang#35196)
oxinabox · Apr 8, 2020 · 4abc4fa · 4abc4fa
1 parent 7bbdeb3
commit 4abc4fa
Showing 1 changed file with 10 additions and 0 deletions.
diff --git a/stdlib/LinearAlgebra/test/tridiag.jl b/stdlib/LinearAlgebra/test/tridiag.jl
@@ -481,4 +481,14 @@ end
     @test sum(SymTridiagonal([1,2,3], [1,2])) == 12
 end
 
+@testset "Issue #28994 (sum of Tridigonal and UniformScaling)" begin
+    dl = [1., 1.]
+    d = [-2., -2., -2.]
+    T = Tridiagonal(dl, d, dl)
+    S = SymTridiagonal(T)
+
+    @test diag(T + 2I) == zero(d)
+    @test diag(S + 2I) == zero(d)
+end
+
 end # module TestTridiagonal