Apply suggestions from code review

Co-authored-by: David Widmann <devmotion@users.noreply.github.com>

Author: gaurav-arya

src/TestUtils.jl

@@ -78,15 +78,19 @@ function test_fft_backend(array_constructor; test_real=true, test_inplace=true)
             # FFT
             y = AbstractFFTs.fft(x_complex, dims)
             @test y ≈ fftw_fft
-            test_inplace && (@test AbstractFFTs.fft!(copy(x_complex), dims) ≈ fftw_fft)
+            if test_inplace
+                @test AbstractFFTs.fft!(copy(x_complex), dims) ≈ fftw_fft
+            end
             # test plan_fft and also inv and plan_inv of plan_ifft, which should all give 
             # functionally identical plans
             plans_to_test = [plan_fft(x, dims), inv(plan_ifft(x, dims)), 
                              AbstractFFTs.plan_inv(plan_ifft(x, dims))]
             for P in plans_to_test
                 @test mul!(similar(y), P, copy(x_complex)) ≈ fftw_fft
             end
-            test_inplace && (plans_to_test = vcat(plans_to_test, plan_fft!(similar(x_complex), dims)))
+            if test_inplace
+                push!(plans_to_test, plan_fft!(similar(x_complex), dims))
+            end
             for P in plans_to_test 
                 @test eltype(P) <: Complex
                 @test P * copy(x_complex) ≈ fftw_fft
@@ -97,12 +101,16 @@ function test_fft_backend(array_constructor; test_real=true, test_inplace=true)
             # BFFT
             fftw_bfft = prod(size(x_complex, d) for d in dims) .* x_complex
             @test AbstractFFTs.bfft(y, dims) ≈ fftw_bfft
-            test_inplace && (@test AbstractFFTs.bfft!(copy(y), dims) ≈ fftw_bfft)
-            plans_to_test = [plan_bfft(similar(y), dims)]
-            for P in plans_to_test
-                @test mul!(similar(x_complex), P, copy(y)) ≈ fftw_bfft
+            if test_inplace
+                @test AbstractFFTs.bfft!(copy(y), dims) ≈ fftw_bfft
+            end
+            P = plan_bfft(similar(y), dims)
+            @test mul!(similar(x_complex), P, copy(y)) ≈ fftw_bfft
+            plans_to_test = if test_inplace
+                [P, plan_bfft!(similar(y), dims)]
+            else
+                [P]
             end
-            test_inplace && (plans_to_test = vcat(plans_to_test, plan_bfft!(similar(y), dims)))
             for P in plans_to_test
                 @test eltype(P) <: Complex
                 @test P * copy(y) ≈ fftw_bfft
@@ -113,13 +121,17 @@ function test_fft_backend(array_constructor; test_real=true, test_inplace=true)
             # IFFT
             fftw_ifft = x_complex
             @test AbstractFFTs.ifft(y, dims) ≈ fftw_ifft
-            test_inplace && (@test AbstractFFTs.ifft!(copy(y), dims) ≈ fftw_ifft)
+            if test_inplace
+                @test AbstractFFTs.ifft!(copy(y), dims) ≈ fftw_ifft
+            end
             plans_to_test = [plan_ifft(x, dims), inv(plan_fft(x, dims)), 
                              AbstractFFTs.plan_inv(plan_fft(x, dims))]
             for P in plans_to_test
                 @test mul!(similar(x_complex), P, copy(y)) ≈ fftw_ifft
             end
-            test_inplace && (plan_to_test = vcat(plans_to_test, plan_ifft!(similar(x_complex), dims)))
+            if test_inplace
+                push!(plans_to_test, plan_ifft!(similar(x_complex), dims))
+            end
             for P in plans_to_test
                 @test eltype(P) <: Complex
                 @test P * copy(y) ≈ fftw_ifft
@@ -130,11 +142,7 @@ function test_fft_backend(array_constructor; test_real=true, test_inplace=true)
             if test_real && real_input
                 x_real = float.(x) # for testing real FFTs
                 # RFFT
-                fftw_rfft = fftw_fft[
-                    (Colon() for _ in 1:(first(dims) - 1))...,
-                    1:(size(fftw_fft, first(dims)) ÷ 2 + 1),
-                    (Colon() for _ in (first(dims) + 1):ndims(fftw_fft))...
-                ]
+                fftw_rfft = selectdim(fftw_fft, first(dims), 1:(size(fftw_fft, first(dims)) ÷ 2 + 1))
                 ry = AbstractFFTs.rfft(x_real, dims)
                 @test ry ≈ fftw_rfft
                 for P in [plan_rfft(similar(x_real), dims), inv(plan_irfft(similar(ry), size(x, first(dims)), dims)),