diff --git a/test/test_module_evaluation.jl b/test/test_module_evaluation.jl
index 0d81e39..4e2f101 100644
--- a/test/test_module_evaluation.jl
+++ b/test/test_module_evaluation.jl
@@ -1,21 +1,48 @@
-# TODO: test `clear_module!`
+@testset "evaluation module" begin
+    function mock_output(document, mod = nothing)
+        parsed = Weave.parse_doc(document, "markdown")
+        doc = Weave.WeaveDoc("dummy.jmd", parsed, Dict())
+        result_doc = run_doc(doc, mod = mod)
+        @test isdefined(result_doc.chunks[1], :output)
+        return result_doc.chunks[1].output
+    end
 
-function mock_output(document, mod = nothing)
-    parsed = Weave.parse_doc(document, "markdown")
-    doc = Weave.WeaveDoc("dummy.jmd", parsed, Dict())
-    result_doc = run_doc(doc, mod = mod)
-    @test isdefined(result_doc.chunks[1], :output)
-    return result_doc.chunks[1].output
+    document = """
+    ```julia
+    @__MODULE__
+    ```
+    """
+
+    # in sandbox
+    @test occursin(r"\#+WeaveSandBox[\#\d]+", mock_output(document))
+
+    # in Main
+    @test strip(mock_output(document, Main)) == "Main"
 end
 
-document = """
-```julia
-@__MODULE__
-```
-"""
+@testset "clear_module!" begin
+    ary = rand(1000000)
+    size = Base.summarysize(ary)
 
-# in sandbox
-@test occursin(r"\#+WeaveSandBox[\#\d]+", mock_output(document))
+    # simple case
+    m = Core.eval(@__MODULE__, :(module $(gensym(:WeaveTestModule)) end))
+    Core.eval(m, :(a = $ary))
+    Weave.clear_module!(m)
+    @test Base.summarysize(m) < size
 
-# in Main
-@test strip(mock_output(document, Main)) == "Main"
+    # recursive case
+    m = Core.eval(@__MODULE__, :(module $(gensym(:WeaveTestModule)) end))
+    Core.eval(m, :(
+        module $(gensym(:WeaveTestSubModule))
+        a = $ary
+        end
+    ))
+    Weave.clear_module!(m)
+    @test Base.summarysize(m) < size
+
+    # doesn't work with constants
+    m = Core.eval(@__MODULE__, :(module $(gensym(:WeaveTestModule)) end))
+    Core.eval(m, :(const a = $ary))
+    Weave.clear_module!(m)
+    @test_broken Base.summarysize(m) < size
+end