Add InverseFunctions.test_inverse

Author: devmotion

Project.toml

@@ -3,13 +3,13 @@ uuid = "3587e190-3f89-42d0-90ee-14403ec27112"
 version = "0.1.0"
 
 [deps]
+Test = "8dfed614-e22c-5e08-85e1-65c5234f0b40"
 
 [compat]
 julia = "1"
 
 [extras]
 Documenter = "e30172f5-a6a5-5a46-863b-614d45cd2de4"
-Test = "8dfed614-e22c-5e08-85e1-65c5234f0b40"
 
 [targets]
-test = ["Documenter", "Test"]
+test = ["Documenter"]

src/InverseFunctions.jl

@@ -6,6 +6,9 @@ Lightweight package that defines an interface to invert functions.
 """
 module InverseFunctions
 
+using Test
+
 include("inverse.jl")
+include("test.jl")
 
 end # module

src/inverse.jl

@@ -45,6 +45,8 @@ true
 Implementations of `inverse(::typeof(f))` have to satisfy
 * `inverse(f)(f(x)) ≈ x` for all `x` in the domain of `f`, and
 * `inverse(inverse(f)) === f`.
+
+You can check your implementation with [`InverseFunctions.test_inverse`](@ref).
 """
 inverse(f)
 export inverse

src/test.jl

@@ -0,0 +1,19 @@
+"""
+    InverseFunctions.test_inverse(f, x; kwargs...)
+
+Check if [`inverse(f)`](@ref) is implemented correctly.
+
+The function checks if
+- `inverse(f)(f(x)) ≈ x` and
+- `inverse(inverse(f)) === f`.
+
+All keyword arguments are passed to `isapprox`.
+"""
+function test_inverse(f, x; kwargs...)
+    @testset "test_inverse: $f with input $x" begin
+        inverse_f = inverse(f)
+        @test isapprox(inverse_f(f(x)), x; kwargs...)
+        @test inverse(inverse_f) === f
+    end
+    return nothing
+end