Add a few tests for generic LinearAlgebra (#40794)

stdlib/LinearAlgebra/test/generic.jl

@@ -142,6 +142,10 @@ end
         @testset "Scaling with 5-argument mul!" begin
             @test mul!(copy(a), 5., a, 10, 100) == a*150
             @test mul!(copy(a), a, 5., 10, 100) == a*150
+            @test mul!(vec(copy(a)), 5., a, 10, 100) == vec(a*150)
+            @test mul!(vec(copy(a)), a, 5., 10, 100) == vec(a*150)
+            @test_throws DimensionMismatch mul!([vec(copy(a)); 0], 5., a, 10, 100)
+            @test_throws DimensionMismatch mul!([vec(copy(a)); 0], a, 5., 10, 100)
             @test mul!(copy(a), Diagonal([1.; 2.]), a, 10, 100) == 10a.*[1; 2] .+ 100a
             @test mul!(copy(a), Diagonal([1; 2]), a, 10, 100)   == 10a.*[1; 2] .+ 100a
             @test mul!(copy(a), a, Diagonal(1.:an), 10, 100) == 10a.*Vector(1:an)' .+ 100a
@@ -189,6 +193,7 @@ end
         @test det(a) == a
         @test norm(a) == abs(a)
         @test norm(a, 0) == 1
+        @test norm(0, 0) == 0
     end
 
     @test !issymmetric(NaN16)
@@ -241,12 +246,14 @@ end
     rotate!(x, y, c, s)
     @test x ≈ c*x2 + s*y2
     @test y ≈ -conj(s)*x2 + c*y2
+    @test_throws DimensionMismatch rotate!([x; x], y, c, s)
 
     x3 = copy(x)
     y3 = copy(y)
     reflect!(x, y, c, s)
     @test x ≈ c*x3 + s*y3
     @test y ≈ conj(s)*x3 - c*y3
+    @test_throws DimensionMismatch reflect!([x; x], y, c, s)
 end
 
 @testset "LinearAlgebra.axp(b)y! for element type without commutative multiplication" begin
@@ -270,6 +277,7 @@ end
     ry = [2 8]
     @test LinearAlgebra.axpy!(α, x, rx, y, ry) == [1 1 1 1; 11 1 1 26]
 end
+
 @testset "norm and normalize!" begin
     vr = [3.0, 4.0]
     for Tr in (Float32, Float64)