diff --git a/test/results/results_eigenvalues.jl b/test/results/results_eigenvalues.jl
index b37b79b4c..c7cb82601 100644
--- a/test/results/results_eigenvalues.jl
+++ b/test/results/results_eigenvalues.jl
@@ -971,3 +971,15 @@ test58_eigvals_GateFlag = [
     -0.19849913626541832 + 0.17939599481963514im
     -0.04238523317744444 + 0.0im
 ]
+
+test59_eigvals = [
+    -99.69916689593907 + 0.0im
+    -84.05122388240402 + 0.0im
+    -39.79684261365684 + 0.0im
+    -38.3444969887499 + 0.0im
+    -8.550153616541023 + 0.0im
+    -0.6772738854081002 - 8.637736379730404im
+    -0.6772738854081002 + 8.637736379730404im
+    -0.36823401395037775 - 0.5649228138733879im
+    -0.36823401395037775 + 0.5649228138733879im
+]
diff --git a/test/results/results_initial_conditions.jl b/test/results/results_initial_conditions.jl
index d54376ab5..cb38572b8 100644
--- a/test/results/results_initial_conditions.jl
+++ b/test/results/results_initial_conditions.jl
@@ -1781,3 +1781,28 @@ test58_x0_init_GateFlag = Dict(
         2.099999999999999
     ],
 )
+
+test59_x0_init = Dict(
+    "V_R" => [
+        1.05
+        1.0198615749401696
+        0.9817964461177487
+    ],
+    "V_I" => [
+        0.0
+        -0.01680380791834505
+        -0.15145839832533242
+    ],
+    "generator-102-1" => [
+        0.8084146853601003
+        0.5302614530689579
+        0.7288775579091268
+        0.7311890654084042
+        0.9615873122791483
+        1.0
+        1.0199999999999998
+        0.047279162537359226
+        0.0
+        2.153115531256307
+    ],
+)
diff --git a/test/test_case59_st6b.jl b/test/test_case59_st6b.jl
new file mode 100644
index 000000000..5ccb57311
--- /dev/null
+++ b/test/test_case59_st6b.jl
@@ -0,0 +1,157 @@
+"""
+Validation PSSE/ST6B:
+This case study defines a three bus system with an infinite bus, GENROU and a load.
+The GENROU machine has connected an ST6B Excitation System.
+The fault drop the line connecting the infinite bus and GENROU.
+"""
+##################################################
+############### LOAD DATA ########################
+##################################################
+
+raw_file = joinpath(TEST_FILES_DIR, "benchmarks/psse/ST6B/ThreeBusMulti.raw")
+dyr_file = joinpath(TEST_FILES_DIR, "benchmarks/psse/ST6B/ThreeBus_ST6B.dyr")
+#csv_file = joinpath(TEST_FILES_DIR, "benchmarks/psse/ST6B/results_PSSe.csv")
+
+@testset "Test 59 ST6B ResidualModel" begin
+    path = joinpath(pwd(), "test-psse-ST6B")
+    !isdir(path) && mkdir(path)
+    try
+        # Define system
+        sys = System(raw_file, dyr_file)
+        for l in get_components(PSY.StandardLoad, sys)
+            transform_load_to_constant_impedance(l)
+        end
+
+        # Define Simulation Problem
+        sim = Simulation(
+            ResidualModel,
+            sys, #system
+            path,
+            (0.0, 20.0), #time span
+            BranchTrip(1.0, Line, "BUS 1-BUS 2-i_1"), #Type of Fault
+        )
+
+        # Test Initial Condition
+        diff_val = [0.0]
+        res = get_init_values_for_comparison(sim)
+        for (k, v) in test59_x0_init
+            diff_val[1] += LinearAlgebra.norm(res[k] - v)
+        end
+
+        @test diff_val[1] < 1e-3
+
+        # Obtain small signal results for initial conditions
+        small_sig = small_signal_analysis(sim)
+        eigs = small_sig.eigenvalues
+        @test small_sig.stable
+
+        # Test Eigenvalues
+        @test LinearAlgebra.norm(eigs - test59_eigvals) < 1e-3
+
+        # Solve problem
+        @test execute!(sim, IDA(); dtmax = 0.005, saveat = 0.005) ==
+              PSID.SIMULATION_FINALIZED
+        results = read_results(sim)
+
+        # Obtain results
+
+        t_psid, v2_psid = get_voltage_magnitude_series(results, 102)
+        _, v3_psid = get_voltage_magnitude_series(results, 103)
+        _, ω_psid = get_state_series(results, ("generator-102-1", :ω))
+        _, Vf = get_field_voltage_series(results, "generator-102-1")
+
+        #=
+        # Obtain PSSE results
+        M = get_csv_data(csv_file)
+        t_psse = M[:, 1]
+        v1_psse = M[:, 2]
+        v2_psse = M[:, 3]
+        v3_psse = M[:, 4]
+        v4_psse = M[:, 5]
+        ω_psse = M[:, 6] .+ 1.0
+        efd_psse = M[:, 7]
+
+        # Test Transient Simulation Results
+
+        @test LinearAlgebra.norm(t_psid - round.(t_psse, digits = 3)) == 0.0
+        @test LinearAlgebra.norm(v2_psid - v2_psse, Inf) <= 1e-3
+        @test LinearAlgebra.norm(v3_psid - v3_psse, Inf) <= 1e-3
+        @test LinearAlgebra.norm(ω_psid - ω_psse, Inf) <= 1e-3
+        =#
+    finally
+        @info("removing test files")
+        rm(path; force = true, recursive = true)
+    end
+end
+
+@testset "Test 59 ST6B MassMatrixModel" begin
+    path = joinpath(pwd(), "test-psse-ST6B")
+    !isdir(path) && mkdir(path)
+    try
+        # Define system
+        sys = System(raw_file, dyr_file)
+        for l in get_components(PSY.StandardLoad, sys)
+            transform_load_to_constant_impedance(l)
+        end
+
+        # Define Simulation Problem
+        sim = Simulation(
+            MassMatrixModel,
+            sys, #system
+            path,
+            (0.0, 20.0), #time span
+            BranchTrip(1.0, Line, "BUS 1-BUS 2-i_1"), #Type of Fault
+        )
+
+        # Test Initial Condition
+        diff_val = [0.0]
+        res = get_init_values_for_comparison(sim)
+        for (k, v) in test59_x0_init
+            diff_val[1] += LinearAlgebra.norm(res[k] - v)
+        end
+
+        @test diff_val[1] < 1e-3
+
+        # Obtain small signal results for initial conditions
+        small_sig = small_signal_analysis(sim)
+        eigs = small_sig.eigenvalues
+        @test small_sig.stable
+
+        # Test Eigenvalues
+        @test LinearAlgebra.norm(eigs - test59_eigvals) < 1e-3
+
+        # Solve problem
+        @test execute!(sim, Rodas4(); dtmax = 0.005, saveat = 0.005) ==
+              PSID.SIMULATION_FINALIZED
+        results = read_results(sim)
+
+        # Obtain results
+
+        t_psid, v2_psid = get_voltage_magnitude_series(results, 102)
+        _, v3_psid = get_voltage_magnitude_series(results, 103)
+        _, ω_psid = get_state_series(results, ("generator-102-1", :ω))
+        _, Vf = get_field_voltage_series(results, "generator-102-1")
+
+        #=
+        # Obtain PSSE results
+        M = get_csv_data(csv_file)
+        t_psse = M[:, 1]
+        v1_psse = M[:, 2]
+        v2_psse = M[:, 3]
+        v3_psse = M[:, 4]
+        v4_psse = M[:, 5]
+        ω_psse = M[:, 6] .+ 1.0
+        efd_psse = M[:, 7]
+
+        # Test Transient Simulation Results
+
+        @test LinearAlgebra.norm(t_psid - round.(t_psse, digits = 3)) == 0.0
+        @test LinearAlgebra.norm(v2_psid - v2_psse, Inf) <= 1e-3
+        @test LinearAlgebra.norm(v3_psid - v3_psse, Inf) <= 1e-3
+        @test LinearAlgebra.norm(ω_psid - ω_psse, Inf) <= 1e-3
+        =#
+    finally
+        @info("removing test files")
+        rm(path; force = true, recursive = true)
+    end
+end