diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index ac1e885e..568d8e48 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -15,6 +15,11 @@ env:
   TEST_MLJBASE: "true"
 jobs:
   test:
+    services:
+      mlflow:
+        image: adacotechjp/mlflow:2.3.1
+        ports:
+          - 5000:5000
     name: Julia ${{ matrix.version }} - ${{ matrix.os }} - ${{ matrix.arch }} - ${{ github.event_name }}
     runs-on: ${{ matrix.os }}
     timeout-minutes: 60
diff --git a/Project.toml b/Project.toml
index a5829d3c..792a7ca5 100644
--- a/Project.toml
+++ b/Project.toml
@@ -68,4 +68,4 @@ Test = "8dfed614-e22c-5e08-85e1-65c5234f0b40"
 TypedTables = "9d95f2ec-7b3d-5a63-8d20-e2491e220bb9"
 
 [targets]
-test = ["DataFrames", "DecisionTree", "Distances", "Logging", "MultivariateStats", "NearestNeighbors", "StableRNGs", "Test", "TypedTables"]
+test = ["DataFrames", "DecisionTree", "Distances", "Logging", "MultivariateStats", "NearestNeighbors", "StableRNGs", "Test", "TypedTables", "MLFlowClient"]
diff --git a/ext/LoggersExt/LoggersExt.jl b/ext/LoggersExt/LoggersExt.jl
index 7d722512..cc4d882f 100644
--- a/ext/LoggersExt/LoggersExt.jl
+++ b/ext/LoggersExt/LoggersExt.jl
@@ -1,10 +1,11 @@
 module LoggersExt
 
 using MLJBase: info, name, Model,
-               params, Machine, Measure,
-               flat_params
+               Machine, Measure, flat_params
 
-import MLJBase: save, evaluate!, MLFlowLogger
+import MLJBase: save, evaluate!, mlflow_logger
+
+include("utils.jl")
 
 include("mlflow.jl")
 
diff --git a/ext/LoggersExt/mlflow.jl b/ext/LoggersExt/mlflow.jl
index d066de18..a793c982 100644
--- a/ext/LoggersExt/mlflow.jl
+++ b/ext/LoggersExt/mlflow.jl
@@ -2,14 +2,14 @@ using MLFlowClient: MLFlow, logparam, logmetric,
                     createrun, MLFlowRun, updaterun,
                     logartifact, getorcreateexperiment
 
-struct MLFlowInstance
+struct MLFlowLogger
     client::MLFlow
     experiment_name::String
     artifact_location::Union{String, Missing}
 end
-MLFlowLogger(base_uri::String, experiment_name::String,
+mlflow_logger(base_uri::String, experiment_name::String,
     artifact_location::Union{String, Missing}) =
-    MLFlowInstance(MLFlow(base_uri), experiment_name, artifact_location)
+    MLFlowLogger(MLFlow(base_uri), experiment_name, artifact_location)
 
 function _logmodelparams(client::MLFlow, run::MLFlowRun, model::Model)
     model_params = params(model) |> flat_params |> collect
@@ -18,8 +18,8 @@ function _logmodelparams(client::MLFlow, run::MLFlowRun, model::Model)
     end
 end
 
-function _logmachinemeasures(client::MLFlow, run::MLFlowRun, measures::Vector{Measure},
-                             measurements::Vector{Float64})
+function _logmachinemeasures(client::MLFlow, run::MLFlowRun, measures::Vector{T},
+                             measurements::Vector{Float64}) where T<:Measure
     measure_names = measures .|> info .|> x -> x.name
     for (name, value) in zip(measure_names, measurements)
         logmetric(client, run, name, value)
@@ -29,7 +29,7 @@ end
 function evaluate!(mach::Machine, resampling, weights,
                    class_weights, rows, verbosity,
                    repeats, measures, operations,
-                   acceleration, force, logger::MLFlowInstance)
+                   acceleration, force, logger::MLFlowLogger)
     performance_evaluation = evaluate!(mach, resampling, weights,
                                        class_weights, rows, verbosity,
                                        repeats, measures, operations,
@@ -46,10 +46,11 @@ function evaluate!(mach::Machine, resampling, weights,
     return performance_evaluation
 end
 
-function save(logger::MLFlowInstance, mach::Machine)
+function save(logger::MLFlowLogger, mach::Machine)
+    io = IOBuffer()
+    save(io, mach)
+
     model_name = name(mach.model)
-    fname = "$(model_name).jls"
-    save(fname, mach)
 
     experiment = getorcreateexperiment(logger.client, logger.experiment_name,
         artifact_location=logger.artifact_location)
@@ -57,6 +58,7 @@ function save(logger::MLFlowInstance, mach::Machine)
         run_name="$(model_name) run")
 
     _logmodelparams(logger.client, run, mach.model)
-    logartifact(logger.client, run, fname)
-    rm(fname)
+    fname = "$(model_name).jls"
+    logartifact(logger.client, run, fname, io)
+    updaterun(logger.client, run, "FINISHED")
 end
diff --git a/src/parameter_inspection.jl b/ext/LoggersExt/utils.jl
similarity index 68%
rename from src/parameter_inspection.jl
rename to ext/LoggersExt/utils.jl
index f58864e4..2bb63749 100644
--- a/src/parameter_inspection.jl
+++ b/ext/LoggersExt/utils.jl
@@ -1,19 +1,19 @@
-istransparent(::Any) = false
-istransparent(::MLJType) = true
+isamodel(::Any) = false
+isamodel(::Model) = true
 
 """
-    params(m::MLJType)
+    params(m::Model)
 
 Recursively convert any transparent object `m` into a named tuple,
 keyed on the property names of `m`. An object is *transparent* if
-`MLJBase.istransparent(m) == true`. The named tuple is possibly nested
+`isamodel(m) == true`. The named tuple is possibly nested
 because `params` is recursively applied to the property values, which
 themselves might be transparent.
 
-For most `MLJType` objects, properties are synonymous with fields, but
+For most `Model` objects, properties are synonymous with fields, but
 this is not a hard requirement.
 
-Most objects of type `MLJType` are transparent.
+Most objects of type `Model` are transparent.
 
     julia> params(EnsembleModel(atom=ConstantClassifier()))
     (atom = (target_type = Bool,),
@@ -24,7 +24,7 @@ Most objects of type `MLJType` are transparent.
      parallel = true,)
 
 """
-params(m) = params(m, Val(istransparent(m)))
+params(m) = params(m, Val(isamodel(m)))
 params(m, ::Val{false}) = m
 function params(m, ::Val{true})
     fields = propertynames(m)
diff --git a/src/MLJBase.jl b/src/MLJBase.jl
index ffa0aac0..ae895a19 100644
--- a/src/MLJBase.jl
+++ b/src/MLJBase.jl
@@ -294,11 +294,15 @@ export coerce, coerce!, autotype, schema, info
 export UnivariateFiniteArray, UnivariateFiniteVector
 
 # -----------------------------------------------------------------------
-# abstract model types defined in MLJModelInterface.jl and extended here:
+# re-export from MLJModelInterface.jl
+
+#abstract model types defined in MLJModelInterface.jl and extended here:
 for T in EXTENDED_ABSTRACT_MODEL_TYPES
     @eval(export $T)
 end
 
+export params
+
 # -------------------------------------------------------------------
 # exports from this module, MLJBase
 
@@ -308,9 +312,6 @@ export default_resource
 # one_dimensional_ranges.jl:
 export ParamRange, NumericRange, NominalRange, iterator, scale
 
-# parameter_inspection.jl:
-export params # note this is *not* an extension of StatsBase.params
-
 # data.jl:
 export partition, unpack, complement, restrict, corestrict
 
@@ -381,7 +382,7 @@ export pdf, sampler, mode, median, mean, shuffle!, categorical, shuffle,
    levels, levels!, std, Not, support, logpdf, LittleDict
 
 # loggers.jl
-export MLFlowLogger
+export mlflow_logger
 
 if !isdefined(Base, :get_extension)
   include("../ext/LoggersExt/LoggersExt.jl")
diff --git a/src/loggers.jl b/src/loggers.jl
index dce7b2d1..c2849b2f 100644
--- a/src/loggers.jl
+++ b/src/loggers.jl
@@ -1,7 +1,8 @@
 """
-    MLFlowLogger(; base_uri="localhost:5000", experiment_name=missing)
+    mlflow_logger(; base_uri="localhost:5000", experiment_name=missing)
 
-Base type for MLFlow logger. Creates an instance of MLFlow, as defined in
+Constructor for the base type for MLFlow logger. Creates an instance of MLFlow,
+as defined in
 [`MLFlowClient.jl`](https://juliaai.github.io/MLFlowClient.jl/dev/), and logs
 to an experiment.
 
@@ -13,14 +14,14 @@ If `experiment_name` is not provided, a new experiment with the name
 "MLJ.jl experiments" will be created.
 
 ### Return value
-A `MLFlowInstance` object, containing a
+A `MLFlowLogger` object, containing a
 [`MLFlow`](https://juliaai.github.io/MLFlowClient.jl/dev/reference/#MLFlowClient.MLFlow)
 object and the experiment name
 
 """
-MLFlowLogger(; base_uri="http://localhost:5000",
+mlflow_logger(; base_uri="http://localhost:5000",
     experiment_name="MLJ experiments",
     artifact_location=missing) =
-    MLFlowLogger(base_uri, experiment_name, artifact_location)
-MLFlowLogger(_, _, _) =
-    error("Please run `import MLFlowClient` to use MLFlowLogger.")
+    mlflow_logger(base_uri, experiment_name, artifact_location)
+mlflow_logger(_, _, _) =
+    error("Please run `import MLFlowClient` to use mlflow_logger.")
diff --git a/src/utilities.jl b/src/utilities.jl
index f19eceec..1dcc0235 100644
--- a/src/utilities.jl
+++ b/src/utilities.jl
@@ -48,14 +48,14 @@ LittleDict{...} with 3 entries:
 "Y"   => 3
 ```
 """
-function flat_params(params::NamedTuple)
+function flat_params(parameters::NamedTuple)
     result = LittleDict{String, Any}()
-    for key in keys(params)
-        value = getproperty(params, key)
+    for key in keys(parameters)
+        value = params(getproperty(parameters, key))
         if value isa NamedTuple
             sub_dict = flat_params(value)
             for (sub_key, sub_value) in pairs(sub_dict)
-                new_key = string(key, "_", sub_key)
+                new_key = string(key, "__", sub_key)
                 result[new_key] = sub_value
             end
         else
diff --git a/test/extensions/loggers.jl b/test/extensions/loggers.jl
new file mode 100644
index 00000000..64d2830d
--- /dev/null
+++ b/test/extensions/loggers.jl
@@ -0,0 +1,60 @@
+module TestLoggers
+
+using Test
+using MLJBase
+using ..Models
+
+@testset "mlflow logger" begin
+    artifact_directory = "mlj-test"
+    experiment_name = "mlflow logger tests"
+
+    @testset "outside extension tests" begin
+        @test_throws ErrorException mlflow_logger()
+
+        using MLFlowClient
+        logger = mlflow_logger(; experiment_name=experiment_name, artifact_location=artifact_directory)
+
+        @test logger.client isa MLFlow
+        @test logger.experiment_name == experiment_name
+        @test logger.artifact_location == artifact_directory
+    end # @testset "outside extension tests"
+
+    @testset "extension tests" begin
+        X = (x=rand(4),)
+        y = ["Chenta", "Missy", "Gala", "Wendy"] |> categorical
+
+        mach = machine(ConstantClassifier(), X, y)
+        fit!(mach, verbosity=0)
+
+        logger = mlflow_logger(; experiment_name=experiment_name, artifact_location=artifact_directory)
+
+        @testset "save" begin
+            run = MLJBase.save(logger, mach)
+            experiment = getexperiment(logger.client, run.info.experiment_id)
+            @test run isa MLFlowRun
+            @test experiment isa MLFlowExperiment
+
+            deleterun(logger.client, run)
+            deleteexperiment(logger.client, experiment)
+        end # @testset "save"
+
+        @testset "evaluate!" begin
+            evaluate!(mach, resampling=Holdout(), logger=logger)
+
+            experiments = searchexperiments(logger.client)
+            experiments_ids = experiments .|> (e -> e.experiment_id)
+            runs = searchruns(logger.client, experiments_ids)
+
+            # it's 2 because of the default experiment
+            @test length(experiments_ids) == 2
+            @test length(runs) == 1
+
+            deleterun(logger.client, runs[1])
+            deleteexperiment(logger.client, experiments[2])
+        end # @testset "evaluate!"
+    end # @testset "extension tests"
+end # @testset "mlflow logger"
+
+end # module
+
+true
diff --git a/test/runtests.jl b/test/runtests.jl
index 8b07929e..a55c5d19 100644
--- a/test/runtests.jl
+++ b/test/runtests.jl
@@ -80,3 +80,7 @@ end
     @test include("hyperparam/one_dimensional_ranges.jl")
     @test include("hyperparam/one_dimensional_range_methods.jl")
 end
+
+@conditional_testset "extensions" begin
+    @test include("extensions/loggers.jl")
+end