🚨 Increase test coverage

test/gravity_models.jl

@@ -4,6 +4,33 @@
 #
 ############################################################################################
 
+# == File: ./src/GravityModels/api.jl ======================================================
+
+@testset "API" verbose = true begin
+    dt_J2000 = DateTime("2000-01-01T12:00:00.000")
+
+    # We will fetch the EIGEN-6C model that has time dependent coefficients.
+    eigen6c_file = fetch_icgem_file(
+        "http://icgem.gfz-potsdam.de/getmodel/gfc/0776caed6c65af24051697a65147b59e436cb464cb0930c1863fee6ecfbc31b0/EIGEN-6C.gfc"
+    )
+
+    eigen6c = GravityModels.load(IcgemFile, eigen6c_file)
+
+    time = Dates.value(DateTime("2023-06-19") - dt_J2000) / 1000
+
+    Clm_expected, Slm_expected = GravityModels.coefficients(eigen6c, 2, 2, time)
+    Clm, Slm = GravityModels.coefficients(eigen6c, 2, 2, DateTime("2023-06-19"))
+
+    @test Clm == Clm_expected
+    @test Slm == Slm_expected
+
+    Clm_expected, Slm_expected = GravityModels.coefficients(eigen6c, 2, 2, 0)
+    Clm, Slm = GravityModels.coefficients(eigen6c, 2, 2)
+
+    @test Clm == Clm_expected
+    @test Slm == Slm_expected
+end
+
 # == File: ./src/GravityModels/accelerations.jl ============================================
 
 # TODO: Add tests with a model that has time-varying coefficients.
@@ -79,8 +106,31 @@ end
 
 # == File: ./src/GravityModels/gravitational_field_derivative.jl ===========================
 
-# NOTE: We can skip the gravitational field derivative tests because it is indirectly tested
-# in the previous sections.
+# NOTE: We can skip most of the gravitational field derivative tests because it is
+# indirectly tested in the previous sections.
+
+@testset "Gravity Field Derivative" verbose = true begin
+    dt_J2000 = DateTime("2000-01-01T12:00:00.000")
+
+    # We will fetch the EIGEN-6C model that has time dependent coefficients.
+    eigen6c_file = fetch_icgem_file(
+        "http://icgem.gfz-potsdam.de/getmodel/gfc/0776caed6c65af24051697a65147b59e436cb464cb0930c1863fee6ecfbc31b0/EIGEN-6C.gfc"
+    )
+
+    eigen6c = GravityModels.load(IcgemFile, eigen6c_file)
+    r_itrf = [7000.0e3, 0, 0]
+
+    time = Dates.value(DateTime("2023-06-19") - dt_J2000) / 1000
+    ∂U_∂r_expected, ∂U_∂ϕ_expected, ∂U_∂λ_expected =
+        GravityModels.gravitational_field_derivative(eigen6c, r_itrf, time)
+
+    ∂U_∂r, ∂U_∂ϕ, ∂U_∂λ =
+        GravityModels.gravitational_field_derivative(eigen6c, r_itrf, DateTime("2023-06-19"))
+
+    @test ∂U_∂r == ∂U_∂r_expected
+    @test ∂U_∂ϕ == ∂U_∂ϕ_expected
+    @test ∂U_∂λ == ∂U_∂λ_expected
+end
 
 @testset "Gravity Field Derivative [ERRORS]" verbose = true begin
     egm96 = GravityModels.load(IcgemFile, fetch_icgem_file(:EGM96))