Additional pushfwd and pullbck tests

Author: oschulz

test/combinators/transformedmeasure.jl

@@ -79,3 +79,103 @@ end
         end
     end
 end
+
+using IrrationalConstants: loghalf
+
+@testset "Half" begin
+    μ = Half(StdNormal())
+
+    # Test logdensityof for positive values
+    @test logdensityof(μ, 1.0) ≈ logdensityof(StdNormal(), 1.0) - loghalf
+
+    # Test logdensityof for negative values (should return -Inf)
+    @test logdensityof(μ, -1.0) == -Inf
+
+    # Test logdensityof for zero
+    @test logdensityof(μ, 0.0) ≈ logdensityof(StdNormal(), 0.0) - loghalf
+end
+
+using Test
+using MeasureBase
+using MeasureBase: gettransform
+using InverseFunctions
+using StaticArrays
+using ChangesOfVariables
+
+@testset "PushforwardMeasure" begin
+    # Test basic pushforward construction
+    μ = StdNormal()
+    f = exp
+    ν = pushfwd(f, μ)
+
+    @test ν isa PushforwardMeasure
+
+    # TODO: How do we access the parent?
+    # @test parent(ν) === μ
+    @test gettransform(ν) === f
+
+    # Test logdensity with AdaptRootMeasure
+    x = 0.5
+    y = f(x)
+    ld = logdensityof(ν, y)
+    @test !isnan(ld)
+    @test isfinite(ld)
+
+    # Test logdensity with PushfwdRootMeasure
+    ν_no_corr = pushfwd(f, μ, PushfwdRootMeasure())
+    ld_no_corr = logdensityof(ν_no_corr, y)
+    @test !isnan(ld_no_corr)
+    @test isfinite(ld_no_corr)
+
+    # Test non-bijective pushforward
+    g = x -> x^2
+    @test_throws ArgumentError logdensityof(pushfwd(g, μ), 1.0)
+    @test_throws ArgumentError logdensityof(pushfwd(g, μ, PushfwdRootMeasure()), 1.0)
+
+    # Test edge cases for _combine_logd_with_ladj
+    @test MeasureBase._combine_logd_with_ladj(-Inf, Inf) == -Inf  # Zero density wins
+    @test MeasureBase._combine_logd_with_ladj(1.0, -Inf) ≈ MeasureBase.near_neg_inf(Float64)
+
+    # Test composition of pushforwards
+    h = x -> exp(x)
+    ν_comp = pushfwd(h, ν)
+    @test ν_comp isa PushforwardMeasure
+
+    # TODO: How do we access the parent?
+    # @test parent(ν_comp) === μ
+
+    # Test identity pushforward
+    ν_id = pushfwd(identity, μ)
+    @test ν_id === μ
+
+    # Test rootmeasure behavior
+    @test rootmeasure(ν) === rootmeasure(μ)  # AdaptRootMeasure
+    @test rootmeasure(ν_no_corr) isa PushforwardMeasure  # PushfwdRootMeasure
+
+    # Test basemeasure
+    @test basemeasure(ν) isa PushforwardMeasure
+    @test basemeasure(ν).style isa PushfwdRootMeasure
+
+    # Test massof
+    # TODO: mass interface is very incomplete
+    # @test massof(ν) == massof(μ)
+
+    # Test rand
+    @test rand(ν) isa Real
+    @test insupport(ν, rand(ν))
+
+    # Test pullback
+    pb = pullbck(f, ν)
+    @test pb isa PushforwardMeasure
+    @test logdensityof(pb, y) ≈ logdensityof(μ, y)
+
+    # Test deprecated pullback
+    @test_deprecated pullback(f, μ)
+end
+
+@testset "PushFwdStyle types" begin
+    @test AdaptRootMeasure() isa PushFwdStyle
+    @test PushfwdRootMeasure() isa PushFwdStyle
+    @test MeasureBase.WithVolCorr === AdaptRootMeasure
+    @test MeasureBase.NoVolCorr === PushfwdRootMeasure
+end