Tweak add_tiny

Project.toml

@@ -1,6 +1,6 @@
 name = "FiniteDifferences"
 uuid = "26cc04aa-876d-5657-8c51-4c34ba976000"
-version = "0.10.7"
+version = "0.10.8"
 
 [deps]
 ChainRulesCore = "d360d2e6-b24c-11e9-a2a3-2a2ae2dbcce4"

src/methods.jl

@@ -12,9 +12,11 @@ const DEFAULT_CONDITION = 100
 """
     add_tiny(x::Real)
 
-Add a tiny number, 10^{-20}, to `x` while preserving its type.
+Add a tiny number, 10^{-20}, to `x`, preserving the type. If `x` is an `Integer`, it is
+promoted to a suitable floating point type.
 """
 add_tiny(x::T) where {T<:Real} = x + convert(T, 1e-20)
+add_tiny(x::Integer) = add_tiny(float(x))
 
 forward_grid(p::Int) = 0:(p - 1)
 backward_grid(p::Int) = (1 - p):0

test/methods.jl

@@ -1,7 +1,17 @@
-using FiniteDifferences: Forward, Backward, Central, Nonstandard
+using FiniteDifferences: Forward, Backward, Central, Nonstandard, add_tiny
 
 @testset "Methods" begin
 
+    @testset "add_tiny" begin
+        @test add_tiny(convert(Float64, 5)) isa Float64
+        @test add_tiny(convert(Float32, 5)) isa Float32
+        @test add_tiny(convert(Float16, 5)) isa Float16
+
+        @test add_tiny(convert(Int, 5)) isa Float64
+        @test add_tiny(convert(UInt, 5)) isa Float64
+        @test add_tiny(convert(Bool, 1)) isa Float64
+    end
+
     # The different approaches to approximating the gradient to try.
     methods = [forward_fdm, backward_fdm, central_fdm]
 
@@ -36,6 +46,11 @@ using FiniteDifferences: Forward, Backward, Central, Nonstandard
         end
     end
 
+    # Integration test to ensure that Integer-output functions can be tested.
+    @testset "Integer Output" begin
+        @test isapprox(central_fdm(5, 1)(x -> 5, 0), 0; rtol=1e-12, atol=1e-12)
+    end
+
     @testset "Adaptation improves estimate" begin
         @test forward_fdm(5, 1)(log, 0.001; adapt=0) ≈ 969.2571703
         @test forward_fdm(5, 1)(log, 0.001; adapt=1) ≈ 1000