diff --git a/src/structuredbroadcast.jl b/src/structuredbroadcast.jl
index f2cfc74a..a8eeaa94 100644
--- a/src/structuredbroadcast.jl
+++ b/src/structuredbroadcast.jl
@@ -84,9 +84,9 @@ function structured_broadcast_alloc(bc, ::Type{Bidiagonal}, ::Type{ElType}, n) w
     return Bidiagonal(Array{ElType}(undef, n),Array{ElType}(undef, n1), uplo)
 end
 structured_broadcast_alloc(bc, ::Type{SymTridiagonal}, ::Type{ElType}, n) where {ElType} =
-    SymTridiagonal(Array{ElType}(undef, n),Array{ElType}(undef, n-1))
+    SymTridiagonal(Array{ElType}(undef, n),Array{ElType}(undef, max(0,n-1)))
 structured_broadcast_alloc(bc, ::Type{Tridiagonal}, ::Type{ElType}, n) where {ElType} =
-    Tridiagonal(Array{ElType}(undef, n-1),Array{ElType}(undef, n),Array{ElType}(undef, n-1))
+    Tridiagonal(Array{ElType}(undef, max(0,n-1)),Array{ElType}(undef, n),Array{ElType}(undef, max(0,n-1)))
 structured_broadcast_alloc(bc, ::Type{LowerTriangular}, ::Type{ElType}, n) where {ElType} =
     LowerTriangular(Array{ElType}(undef, n, n))
 structured_broadcast_alloc(bc, ::Type{UpperTriangular}, ::Type{ElType}, n) where {ElType} =
diff --git a/test/structuredbroadcast.jl b/test/structuredbroadcast.jl
index b8b16a8d..398d0ff5 100644
--- a/test/structuredbroadcast.jl
+++ b/test/structuredbroadcast.jl
@@ -11,160 +11,164 @@ isdefined(Main, :SizedArrays) || @eval Main include(joinpath($(BASE_TEST_PATH),
 using .Main.SizedArrays
 
 @testset "broadcast[!] over combinations of scalars, structured matrices, and dense vectors/matrices" begin
-    N = 10
-    s = rand()
-    fV = rand(N)
-    fA = rand(N, N)
-    Z = copy(fA)
-    D = Diagonal(rand(N))
-    B = Bidiagonal(rand(N), rand(N - 1), :U)
-    T = Tridiagonal(rand(N - 1), rand(N), rand(N - 1))
-    S = SymTridiagonal(rand(N), rand(N - 1))
-    U = UpperTriangular(rand(N,N))
-    L = LowerTriangular(rand(N,N))
-    M = Matrix(rand(N,N))
-    structuredarrays = (D, B, T, U, L, M, S)
-    fstructuredarrays = map(Array, structuredarrays)
-    for (X, fX) in zip(structuredarrays, fstructuredarrays)
-        @test (Q = broadcast(sin, X); typeof(Q) == typeof(X) && Q == broadcast(sin, fX))
-        @test broadcast!(sin, Z, X) == broadcast(sin, fX)
-        @test (Q = broadcast(cos, X); Q isa Matrix && Q == broadcast(cos, fX))
-        @test broadcast!(cos, Z, X) == broadcast(cos, fX)
-        @test (Q = broadcast(*, s, X); typeof(Q) == typeof(X) && Q == broadcast(*, s, fX))
-        @test broadcast!(*, Z, s, X) == broadcast(*, s, fX)
-        @test (Q = broadcast(+, fV, fA, X); Q isa Matrix && Q == broadcast(+, fV, fA, fX))
-        @test broadcast!(+, Z, fV, fA, X) == broadcast(+, fV, fA, fX)
-        @test (Q = broadcast(*, s, fV, fA, X); Q isa Matrix && Q == broadcast(*, s, fV, fA, fX))
-        @test broadcast!(*, Z, s, fV, fA, X) == broadcast(*, s, fV, fA, fX)
-
-        @test X .* 2.0 == X .* (2.0,) == fX .* 2.0
-        @test X .* 2.0 isa typeof(X)
-        @test X .* (2.0,) isa typeof(X)
-        @test isequal(X .* Inf, fX .* Inf)
-
-        two = 2
-        @test X .^ 2 ==  X .^ (2,) == fX .^ 2 == X .^ two
-        @test X .^ 2 isa typeof(X)
-        @test X .^ (2,) isa typeof(X)
-        @test X .^ two isa typeof(X)
-        @test X .^ 0 == fX .^ 0
-        @test X .^ -1 == fX .^ -1
-
-        for (Y, fY) in zip(structuredarrays, fstructuredarrays)
-            @test broadcast(+, X, Y) == broadcast(+, fX, fY)
-            @test broadcast!(+, Z, X, Y) == broadcast(+, fX, fY)
-            @test broadcast(*, X, Y) == broadcast(*, fX, fY)
-            @test broadcast!(*, Z, X, Y) == broadcast(*, fX, fY)
+    @testset for N in (0,1,2,10) # some edge cases, and a structured case
+        s = rand()
+        fV = rand(N)
+        fA = rand(N, N)
+        Z = copy(fA)
+        D = Diagonal(rand(N))
+        B = Bidiagonal(rand(N), rand(max(0,N-1)), :U)
+        T = Tridiagonal(rand(max(0,N-1)), rand(N), rand(max(0,N-1)))
+        S = SymTridiagonal(rand(N), rand(max(0,N-1)))
+        U = UpperTriangular(rand(N,N))
+        L = LowerTriangular(rand(N,N))
+        M = Matrix(rand(N,N))
+        structuredarrays = (D, B, T, U, L, M, S)
+        fstructuredarrays = map(Array, structuredarrays)
+        @testset "$(nameof(typeof(X)))" for (X, fX) in zip(structuredarrays, fstructuredarrays)
+            @test (Q = broadcast(sin, X); typeof(Q) == typeof(X) && Q == broadcast(sin, fX))
+            @test broadcast!(sin, Z, X) == broadcast(sin, fX)
+            @test (Q = broadcast(cos, X); Q isa Matrix && Q == broadcast(cos, fX))
+            @test broadcast!(cos, Z, X) == broadcast(cos, fX)
+            @test (Q = broadcast(*, s, X); typeof(Q) == typeof(X) && Q == broadcast(*, s, fX))
+            @test broadcast!(*, Z, s, X) == broadcast(*, s, fX)
+            @test (Q = broadcast(+, fV, fA, X); Q isa Matrix && Q == broadcast(+, fV, fA, fX))
+            @test broadcast!(+, Z, fV, fA, X) == broadcast(+, fV, fA, fX)
+            @test (Q = broadcast(*, s, fV, fA, X); Q isa Matrix && Q == broadcast(*, s, fV, fA, fX))
+            @test broadcast!(*, Z, s, fV, fA, X) == broadcast(*, s, fV, fA, fX)
+
+            @test X .* 2.0 == X .* (2.0,) == fX .* 2.0
+            @test X .* 2.0 isa typeof(X)
+            @test X .* (2.0,) isa typeof(X)
+            @test isequal(X .* Inf, fX .* Inf)
+
+            two = 2
+            @test X .^ 2 ==  X .^ (2,) == fX .^ 2 == X .^ two
+            @test X .^ 2 isa typeof(X)
+            @test X .^ (2,) isa typeof(X)
+            @test X .^ two isa typeof(X)
+            @test X .^ 0 == fX .^ 0
+            @test X .^ -1 == fX .^ -1
+
+            for (Y, fY) in zip(structuredarrays, fstructuredarrays)
+                @test broadcast(+, X, Y) == broadcast(+, fX, fY)
+                @test broadcast!(+, Z, X, Y) == broadcast(+, fX, fY)
+                @test broadcast(*, X, Y) == broadcast(*, fX, fY)
+                @test broadcast!(*, Z, X, Y) == broadcast(*, fX, fY)
+            end
         end
-    end
-    diagonals = (D, B, T)
-    fdiagonals = map(Array, diagonals)
-    for (X, fX) in zip(diagonals, fdiagonals)
-        for (Y, fY) in zip(diagonals, fdiagonals)
-            @test broadcast(+, X, Y)::Union{Diagonal,Bidiagonal,Tridiagonal} == broadcast(+, fX, fY)
-            @test broadcast!(+, Z, X, Y) == broadcast(+, fX, fY)
-            @test broadcast(*, X, Y)::Union{Diagonal,Bidiagonal,Tridiagonal} == broadcast(*, fX, fY)
-            @test broadcast!(*, Z, X, Y) == broadcast(*, fX, fY)
+        diagonals = (D, B, T)
+        fdiagonals = map(Array, diagonals)
+        for (X, fX) in zip(diagonals, fdiagonals)
+            for (Y, fY) in zip(diagonals, fdiagonals)
+                @test broadcast(+, X, Y)::Union{Diagonal,Bidiagonal,Tridiagonal} == broadcast(+, fX, fY)
+                @test broadcast!(+, Z, X, Y) == broadcast(+, fX, fY)
+                @test broadcast(*, X, Y)::Union{Diagonal,Bidiagonal,Tridiagonal} == broadcast(*, fX, fY)
+                @test broadcast!(*, Z, X, Y) == broadcast(*, fX, fY)
+            end
         end
-    end
-    UU = UnitUpperTriangular(rand(N,N))
-    UL = UnitLowerTriangular(rand(N,N))
-    unittriangulars = (UU, UL)
-    Ttris = typeof.((UpperTriangular(parent(UU)), LowerTriangular(parent(UU))))
-    funittriangulars = map(Array, unittriangulars)
-    for (X, fX, Ttri) in zip(unittriangulars, funittriangulars, Ttris)
-        @test (Q = broadcast(sin, X); typeof(Q) == Ttri && Q == broadcast(sin, fX))
-        @test broadcast!(sin, Z, X) == broadcast(sin, fX)
-        @test (Q = broadcast(cos, X); Q isa Matrix && Q == broadcast(cos, fX))
-        @test broadcast!(cos, Z, X) == broadcast(cos, fX)
-        @test (Q = broadcast(*, s, X); typeof(Q) == Ttri && Q == broadcast(*, s, fX))
-        @test broadcast!(*, Z, s, X) == broadcast(*, s, fX)
-        @test (Q = broadcast(+, fV, fA, X); Q isa Matrix && Q == broadcast(+, fV, fA, fX))
-        @test broadcast!(+, Z, fV, fA, X) == broadcast(+, fV, fA, fX)
-        @test (Q = broadcast(*, s, fV, fA, X); Q isa Matrix && Q == broadcast(*, s, fV, fA, fX))
-        @test broadcast!(*, Z, s, fV, fA, X) == broadcast(*, s, fV, fA, fX)
-
-        @test X .* 2.0 == X .* (2.0,) == fX .* 2.0
-        @test X .* 2.0 isa Ttri
-        @test X .* (2.0,) isa Ttri
-        @test isequal(X .* Inf, fX .* Inf)
-
-        two = 2
-        @test X .^ 2 ==  X .^ (2,) == fX .^ 2 == X .^ two
-        @test X .^ 2 isa typeof(X) # special cased, as isstructurepreserving
-        @test X .^ (2,) isa Ttri
-        @test X .^ two isa Ttri
-        @test X .^ 0 == fX .^ 0
-        @test X .^ -1 == fX .^ -1
-
-        for (Y, fY) in zip(unittriangulars, funittriangulars)
-            @test broadcast(+, X, Y) == broadcast(+, fX, fY)
-            @test broadcast!(+, Z, X, Y) == broadcast(+, fX, fY)
-            @test broadcast(*, X, Y) == broadcast(*, fX, fY)
-            @test broadcast!(*, Z, X, Y) == broadcast(*, fX, fY)
+        UU = UnitUpperTriangular(rand(N,N))
+        UL = UnitLowerTriangular(rand(N,N))
+        unittriangulars = (UU, UL)
+        Ttris = typeof.((UpperTriangular(parent(UU)), LowerTriangular(parent(UU))))
+        funittriangulars = map(Array, unittriangulars)
+        for (X, fX, Ttri) in zip(unittriangulars, funittriangulars, Ttris)
+            @test (Q = broadcast(sin, X); typeof(Q) == Ttri && Q == broadcast(sin, fX))
+            @test broadcast!(sin, Z, X) == broadcast(sin, fX)
+            @test (Q = broadcast(cos, X); Q isa Matrix && Q == broadcast(cos, fX))
+            @test broadcast!(cos, Z, X) == broadcast(cos, fX)
+            @test (Q = broadcast(*, s, X); typeof(Q) == Ttri && Q == broadcast(*, s, fX))
+            @test broadcast!(*, Z, s, X) == broadcast(*, s, fX)
+            @test (Q = broadcast(+, fV, fA, X); Q isa Matrix && Q == broadcast(+, fV, fA, fX))
+            @test broadcast!(+, Z, fV, fA, X) == broadcast(+, fV, fA, fX)
+            @test (Q = broadcast(*, s, fV, fA, X); Q isa Matrix && Q == broadcast(*, s, fV, fA, fX))
+            @test broadcast!(*, Z, s, fV, fA, X) == broadcast(*, s, fV, fA, fX)
+
+            @test X .* 2.0 == X .* (2.0,) == fX .* 2.0
+            @test X .* 2.0 isa Ttri
+            @test X .* (2.0,) isa Ttri
+            @test isequal(X .* Inf, fX .* Inf)
+
+            two = 2
+            @test X .^ 2 ==  X .^ (2,) == fX .^ 2 == X .^ two
+            @test X .^ 2 isa typeof(X) # special cased, as isstructurepreserving
+            @test X .^ (2,) isa Ttri
+            @test X .^ two isa Ttri
+            @test X .^ 0 == fX .^ 0
+            @test X .^ -1 == fX .^ -1
+
+            for (Y, fY) in zip(unittriangulars, funittriangulars)
+                @test broadcast(+, X, Y) == broadcast(+, fX, fY)
+                @test broadcast!(+, Z, X, Y) == broadcast(+, fX, fY)
+                @test broadcast(*, X, Y) == broadcast(*, fX, fY)
+                @test broadcast!(*, Z, X, Y) == broadcast(*, fX, fY)
+            end
         end
-    end
 
-    @testset "type-stability in Bidiagonal" begin
-        B2 = @inferred (B -> .- B)(B)
-        @test B2 isa Bidiagonal
-        @test B2 == -1 * B
-        B2 = @inferred (B -> B .* 2)(B)
-        @test B2 isa Bidiagonal
-        @test B2 == B + B
-        B2 = @inferred (B -> 2 .* B)(B)
-        @test B2 isa Bidiagonal
-        @test B2 == B + B
-        B2 = @inferred (B -> B ./ 1)(B)
-        @test B2 isa Bidiagonal
-        @test B2 == B
-        B2 = @inferred (B -> 1 .\ B)(B)
-        @test B2 isa Bidiagonal
-        @test B2 == B
+        @testset "type-stability in Bidiagonal" begin
+            B2 = @inferred (B -> .- B)(B)
+            @test B2 isa Bidiagonal
+            @test B2 == -1 * B
+            B2 = @inferred (B -> B .* 2)(B)
+            @test B2 isa Bidiagonal
+            @test B2 == B + B
+            B2 = @inferred (B -> 2 .* B)(B)
+            @test B2 isa Bidiagonal
+            @test B2 == B + B
+            B2 = @inferred (B -> B ./ 1)(B)
+            @test B2 isa Bidiagonal
+            @test B2 == B
+            B2 = @inferred (B -> 1 .\ B)(B)
+            @test B2 isa Bidiagonal
+            @test B2 == B
+        end
     end
 end
 
 @testset "broadcast! where the destination is a structured matrix" begin
-    N = 5
-    A = rand(N, N)
-    sA = A + copy(A')
-    D = Diagonal(rand(N))
-    Bu = Bidiagonal(rand(N), rand(N - 1), :U)
-    Bl = Bidiagonal(rand(N), rand(N - 1), :L)
-    T = Tridiagonal(rand(N - 1), rand(N), rand(N - 1))
-    ◣ = LowerTriangular(rand(N,N))
-    ◥ = UpperTriangular(rand(N,N))
-    M = Matrix(rand(N,N))
-
-    @test broadcast!(sin, copy(D), D) == Diagonal(sin.(D))
-    @test broadcast!(sin, copy(Bu), Bu) == Bidiagonal(sin.(Bu), :U)
-    @test broadcast!(sin, copy(Bl), Bl) == Bidiagonal(sin.(Bl), :L)
-    @test broadcast!(sin, copy(T), T) == Tridiagonal(sin.(T))
-    @test broadcast!(sin, copy(◣), ◣) == LowerTriangular(sin.(◣))
-    @test broadcast!(sin, copy(◥), ◥) == UpperTriangular(sin.(◥))
-    @test broadcast!(sin, copy(M), M) == Matrix(sin.(M))
-    @test broadcast!(*, copy(D), D, A) == Diagonal(broadcast(*, D, A))
-    @test broadcast!(*, copy(Bu), Bu, A) == Bidiagonal(broadcast(*, Bu, A), :U)
-    @test broadcast!(*, copy(Bl), Bl, A) == Bidiagonal(broadcast(*, Bl, A), :L)
-    @test broadcast!(*, copy(T), T, A) == Tridiagonal(broadcast(*, T, A))
-    @test broadcast!(*, copy(◣), ◣, A) == LowerTriangular(broadcast(*, ◣, A))
-    @test broadcast!(*, copy(◥), ◥, A) == UpperTriangular(broadcast(*, ◥, A))
-    @test broadcast!(*, copy(M), M, A) == Matrix(broadcast(*, M, A))
-
-    @test_throws ArgumentError broadcast!(cos, copy(D), D) == Diagonal(sin.(D))
-    @test_throws ArgumentError broadcast!(cos, copy(Bu), Bu) == Bidiagonal(sin.(Bu), :U)
-    @test_throws ArgumentError broadcast!(cos, copy(Bl), Bl) == Bidiagonal(sin.(Bl), :L)
-    @test_throws ArgumentError broadcast!(cos, copy(T), T) == Tridiagonal(sin.(T))
-    @test_throws ArgumentError broadcast!(cos, copy(◣), ◣) == LowerTriangular(sin.(◣))
-    @test_throws ArgumentError broadcast!(cos, copy(◥), ◥) == UpperTriangular(sin.(◥))
-    @test_throws ArgumentError broadcast!(+, copy(D), D, A) == Diagonal(broadcast(*, D, A))
-    @test_throws ArgumentError broadcast!(+, copy(Bu), Bu, A) == Bidiagonal(broadcast(*, Bu, A), :U)
-    @test_throws ArgumentError broadcast!(+, copy(Bl), Bl, A) == Bidiagonal(broadcast(*, Bl, A), :L)
-    @test_throws ArgumentError broadcast!(+, copy(T), T, A) == Tridiagonal(broadcast(*, T, A))
-    @test_throws ArgumentError broadcast!(+, copy(◣), ◣, A) == LowerTriangular(broadcast(*, ◣, A))
-    @test_throws ArgumentError broadcast!(+, copy(◥), ◥, A) == UpperTriangular(broadcast(*, ◥, A))
-    @test_throws ArgumentError broadcast!(*, copy(◥), ◣, 2)
-    @test_throws ArgumentError broadcast!(*, copy(Bu), Bl, 2)
+    @testset for N in (0,1,2,5)
+        A = rand(N, N)
+        sA = A + copy(A')
+        D = Diagonal(rand(N))
+        Bu = Bidiagonal(rand(N), rand(max(0,N-1)), :U)
+        Bl = Bidiagonal(rand(N), rand(max(0,N-1)), :L)
+        T = Tridiagonal(rand(max(0,N-1)), rand(N), rand(max(0,N-1)))
+        ◣ = LowerTriangular(rand(N,N))
+        ◥ = UpperTriangular(rand(N,N))
+        M = Matrix(rand(N,N))
+
+        @test broadcast!(sin, copy(D), D) == Diagonal(sin.(D))
+        @test broadcast!(sin, copy(Bu), Bu) == Bidiagonal(sin.(Bu), :U)
+        @test broadcast!(sin, copy(Bl), Bl) == Bidiagonal(sin.(Bl), :L)
+        @test broadcast!(sin, copy(T), T) == Tridiagonal(sin.(T))
+        @test broadcast!(sin, copy(◣), ◣) == LowerTriangular(sin.(◣))
+        @test broadcast!(sin, copy(◥), ◥) == UpperTriangular(sin.(◥))
+        @test broadcast!(sin, copy(M), M) == Matrix(sin.(M))
+        @test broadcast!(*, copy(D), D, A) == Diagonal(broadcast(*, D, A))
+        @test broadcast!(*, copy(Bu), Bu, A) == Bidiagonal(broadcast(*, Bu, A), :U)
+        @test broadcast!(*, copy(Bl), Bl, A) == Bidiagonal(broadcast(*, Bl, A), :L)
+        @test broadcast!(*, copy(T), T, A) == Tridiagonal(broadcast(*, T, A))
+        @test broadcast!(*, copy(◣), ◣, A) == LowerTriangular(broadcast(*, ◣, A))
+        @test broadcast!(*, copy(◥), ◥, A) == UpperTriangular(broadcast(*, ◥, A))
+        @test broadcast!(*, copy(M), M, A) == Matrix(broadcast(*, M, A))
+
+        if N > 2
+            @test_throws ArgumentError broadcast!(cos, copy(D), D)
+            @test_throws ArgumentError broadcast!(cos, copy(Bu), Bu)
+            @test_throws ArgumentError broadcast!(cos, copy(Bl), Bl)
+            @test_throws ArgumentError broadcast!(cos, copy(T), T)
+            @test_throws ArgumentError broadcast!(cos, copy(◣), ◣)
+            @test_throws ArgumentError broadcast!(cos, copy(◥), ◥)
+            @test_throws ArgumentError broadcast!(+, copy(D), D, A)
+            @test_throws ArgumentError broadcast!(+, copy(Bu), Bu, A)
+            @test_throws ArgumentError broadcast!(+, copy(Bl), Bl, A)
+            @test_throws ArgumentError broadcast!(+, copy(T), T, A)
+            @test_throws ArgumentError broadcast!(+, copy(◣), ◣, A)
+            @test_throws ArgumentError broadcast!(+, copy(◥), ◥, A)
+            @test_throws ArgumentError broadcast!(*, copy(◥), ◣, 2)
+            @test_throws ArgumentError broadcast!(*, copy(Bu), Bl, 2)
+        end
+    end
 end
 
 @testset "map[!] over combinations of structured matrices" begin