Add docstring

Author: gaurav-arya

docs/Project.toml

@@ -1,4 +1,5 @@
 [deps]
+AbstractFFTs = "621f4979-c628-5d54-868e-fcf4e3e8185c"
 Documenter = "e30172f5-a6a5-5a46-863b-614d45cd2de4"
 
 [compat]

docs/src/api.md

@@ -26,4 +26,5 @@ AbstractFFTs.ifftshift
 AbstractFFTs.ifftshift!
 AbstractFFTs.fftfreq
 AbstractFFTs.rfftfreq
+AbstractFFTs.TestUtils.test_fft_backend
 ```

src/TestUtils.jl

@@ -11,6 +11,16 @@ using LinearAlgebra
 using Test
 
 """
+    test_fft_backend(array_constructor) 
+
+Run tests to verify correctness of all FFT functions based on a particular 
+backend plan implementation. The backend implementation is assumed to be loaded 
+prior to calling this function.
+
+The input `array_constructor` determines the `AbstractArray` implementation for
+which the correctness tests are run. It is assumed to be a callable object that
+takes in input arrays of type `Array` and return arrays of the desired type for
+testing: this would most commonly be a constructor such as `Array` or `CuArray`.
 """
 function test_fft_backend(array_constructor)
     @testset "fft correctness" begin

test/runtests.jl

@@ -9,8 +9,9 @@ Random.seed!(1234)
 
 include("TestPlans.jl")
 
+# Run tests for FFT plans (and the operations in AbstractFFTs that derive from them)
 using .TestPlans
-test_fft_backend(Array) # Tests for FFT plans (and operations in AbstractFFTs that derive from them)
+test_fft_backend(Array) 
 
 @testset "rfft sizes" begin
     A = rand(11, 10)