Add tests

Author: YingboMa

test/linalg.jl

@@ -6,6 +6,16 @@ b = ArrayPartition(bb)
 @test Array(b) == collect(b) == vcat(bb...)
 A = randn(MersenneTwister(123), n+m, n+m)
 
+for T in (UpperTriangular,)
+    B = T(A)
+    @test B*Array(FF \ b) ≈ b
+    bbb = copy(b)
+    @test ldiv!(bbb, FF, b) === bbb
+    copyto!(bbb, b)
+    @test ldiv!(FF, bbb) === bbb
+    @test B*Array(bbb) ≈ b
+end
+
 for ff in (lu, svd, qr)
     FF = ff(A)
     @test A*(FF \ b) ≈ b