diff --git a/src/nnmf.jl b/src/nnmf.jl
index d17b953..ca85762 100644
--- a/src/nnmf.jl
+++ b/src/nnmf.jl
@@ -32,8 +32,8 @@ function nnmf_model(m::Int = 100, n::Int = 50, k::Int = 10, T::DataType = Float6
   selected = (m * k + 1):((m + n) * k)
 
   function resid!(r, x)
-    W = reshape_array(x[1:(m * k)], (m, k))
-    H = reshape_array(x[(m * k + 1):end], (k, n))
+    W = reshape_array(view(x, 1:(m * k)), (m, k))
+    H = reshape_array(view(x, (m * k + 1):((m + n) * k)), (k, n))
     mul!(WH, W, H)
     for i ∈ eachindex(r)
       r[i] = A[i] - WH[i]
@@ -50,8 +50,8 @@ function nnmf_model(m::Int = 100, n::Int = 50, k::Int = 10, T::DataType = Float6
     resid!(r, x)
     minusR = reshape_array(r, (m, n))
     minusR .*= -1
-    W_T = reshape_array(x[1:(m * k)], (m, k))'
-    H_T = reshape_array(x[(m * k + 1):end], (k, n))'
+    W_T = reshape_array(view(x, 1:(m * k)), (m, k))'
+    H_T = reshape_array(view(x, (m * k + 1):((m + n) * k)), (k, n))'
     mul!(gw, minusR, H_T)
     mul!(gh, W_T, minusR)
     for i ∈ eachindex(gw)
@@ -63,14 +63,56 @@ function nnmf_model(m::Int = 100, n::Int = 50, k::Int = 10, T::DataType = Float6
     return g
   end
 
+  function jacv!(Jv, x, v)
+    W = reshape_array(view(x, 1:(m * k)), (m, k))
+    H = reshape_array(view(x, (m * k + 1):((m + n) * k)), (k, n))
+    W_v = reshape_array(view(v, 1:(m * k)), (m, k))
+    H_v = reshape_array(view(v, (m * k + 1):((m + n) * k)), (k, n))
+    mul!(WH, W_v, H)
+    for i ∈ eachindex(WH)
+      Jv[i] = -WH[i]
+    end
+    mul!(WH, W, H_v)
+    for i ∈ eachindex(WH)
+      Jv[i] -= WH[i]
+    end
+    return Jv
+  end
+
+  function jactv!(Jtv, x, w)
+    W_T = reshape_array(view(x, 1:(m * k)), (m, k))'
+    H_T = reshape_array(view(x, (m * k + 1):((m + n) * k)), (k, n))'
+    X_v = reshape_array(w, (m, n))
+    mul!(gw, X_v, H_T)
+    mul!(gh, W_T, X_v)
+    for i ∈ eachindex(gw)
+      Jtv[i] = -gw[i]
+    end
+    for i ∈ eachindex(gh)
+      Jtv[i + m * k] = -gh[i]
+    end
+    return Jtv
+  end
+  x0 = 3 * rand(eltype(A), k * (m + n))
+
   FirstOrderModel(
     obj,
     grad!,
-    3 * rand(eltype(A), k * (m + n)),
+    x0,
     name = "NNMF",
     lvar = zeros(eltype(A), k * (m + n)),
     uvar = fill!(zeros(eltype(A), k * (m + n)), Inf),
   ),
+  FirstOrderNLSModel(
+    resid!,
+    jacv!,
+    jactv!,
+    m * n,
+    x0,
+    name = "NNMF-LS",
+    lvar = zeros(eltype(A), k * (m + n)),
+    uvar = fill!(zeros(eltype(A), k * (m + n)), Inf),
+  ),
   A[:],
   selected
 end
diff --git a/test/runtests.jl b/test/runtests.jl
index 9ae7bc0..bde6589 100644
--- a/test/runtests.jl
+++ b/test/runtests.jl
@@ -18,6 +18,9 @@ function test_objectives(model, nls_model, x = model.meta.x0)
   g = grad(model, x)
   JtF = jtprod_residual(nls_model, x, F)
   @test all(g .≈ JtF)
+
+  JF = jprod_residual(nls_model, x, x)
+  @test JF' * F ≈ JtF' * x
 end
 
 @testset "BPDN" begin
@@ -137,12 +140,14 @@ end
 end
 
 @testset "NNMF" begin
-  # TODO: complete tests after NLS model has been implemented
   m, n, k = 100, 50, 10
-  model, sol, selected = nnmf_model(m, n, k)
+  model, nls_model, sol, selected = nnmf_model(m, n, k)
   @test selected == (m * k + 1):((m + n) * k)
-  @test typeof(model) <: FirstOrderModel
-  @test typeof(sol) == typeof(model.meta.x0)
+  test_well_defined(model, nls_model, sol)
+  @test nls_model.nls_meta.nequ == m * n
   @test all(model.meta.lvar .== 0)
   @test all(model.meta.uvar .== Inf)
+  @test all(nls_model.meta.lvar .== 0)
+  @test all(nls_model.meta.uvar .== Inf)
+  test_objectives(model, nls_model)
 end