added unit test

Author: simulutions

src/integral_inverses.jl

@@ -41,8 +41,7 @@ struct LinearInterpolationIntInv{uType, tType, itpType, T} <:
     extrapolation_right::ExtrapolationType.T
     iguesser::Guesser{tType}
     itp::itpType
-    function LinearInterpolationIntInv(u, t, A, extrapolation_left,
-            extrapolation_right)
+    function LinearInterpolationIntInv(u, t, A, extrapolation_left, extrapolation_right)
         new{typeof(u), typeof(t), typeof(A), eltype(u)}(
             u, t, extrapolation_left, extrapolation_right, Guesser(t), A)
     end

test/integral_inverse_tests.jl

@@ -1,5 +1,6 @@
 using DataInterpolations
 using DataInterpolations: integral, derivative, invert_integral
+using FiniteDifferences
 
 function test_integral_inverses(method; args = [], kwargs = [])
     A = method(args...; kwargs..., extrapolation = ExtrapolationType.Extension)
@@ -22,17 +23,19 @@ end
 
 function test_integral_inverse_extrapolation()
     # Linear function with constant extrapolation
-    t = collect(0:4)
-    u = [0.0, 2.0, 3.0, 4.0]
+    t = collect(1:4)
+    u = [1.0, 2.0, 3.0, 4.0]
     A = LinearInterpolation(u, t, extrapolation = ExtrapolationType.Constant)
 
-    A_intinv = invert_integral(A, extrapolation_left = ExtrapolationType.Extension,
-        extrapolation_right = ExtrapolationType.Extension)
+    A_intinv = invert_integral(A, ExtrapolationType.Extension, ExtrapolationType.Extension)
 
     # for a linear function, the integral is quadratic
     # but the constant extrapolation part is linear.
-    A_5 = 1 / 2 * 4.0^2 + 5.0
-    @test A_int_inv(A_5) ≈ 5.0
+    area_0_to_4 = 0.5 * 4.0^2
+    area_4_to_5 = 4.0
+    area = area_0_to_4 + area_4_to_5
+
+    @test A_intinv(area) ≈ 5.0
 end
 
 @testset "Linear Interpolation" begin