diff --git a/lib/rexml/functions.rb b/lib/rexml/functions.rb
index 9c226d2cdf..4b46b8e678 100644
--- a/lib/rexml/functions.rb
+++ b/lib/rexml/functions.rb
@@ -315,18 +315,23 @@ module REXML
       end
     end
 
-    # UNTESTED
-    def Functions::boolean( object=nil )
-      if object.kind_of? String
-        if object =~ /\d+/u
-          return object.to_f != 0
-        else
-          return object.size > 0
-        end
-      elsif object.kind_of? Array
-        object = object.find{|x| x and true}
+    def Functions::boolean(object=@@context[:node])
+      case object
+      when true, false
+        object
+      when Float
+        return false if object.zero?
+        return false if object.nan?
+        true
+      when Numeric
+        not object.zero?
+      when String
+        not object.empty?
+      when Array
+        not object.empty?
+      else
+        object ? true : false
       end
-      return object ? true : false
     end
 
     # UNTESTED
diff --git a/test/rexml/test_functions_boolean.rb b/test/rexml/test_functions_boolean.rb
new file mode 100644
index 0000000000..b3e2117c10
--- /dev/null
+++ b/test/rexml/test_functions_boolean.rb
@@ -0,0 +1,75 @@
+# frozen_string_literal: false
+
+require "test/unit"
+require "rexml/document"
+require "rexml/functions"
+
+module REXMLTests
+  class TestFunctionsBoolean < Test::Unit::TestCase
+    def setup
+      REXML::Functions.context = nil
+    end
+
+    def test_true
+      assert_equal(true, REXML::Functions.boolean(true))
+    end
+
+    def test_false
+      assert_equal(false, REXML::Functions.boolean(false))
+    end
+
+    def test_integer_true
+      assert_equal(true, REXML::Functions.boolean(1))
+    end
+
+    def test_integer_positive_zero
+      assert_equal(false, REXML::Functions.boolean(0))
+    end
+
+    def test_integer_negative_zero
+      assert_equal(false, REXML::Functions.boolean(-0))
+    end
+
+    def test_float_true
+      assert_equal(true, REXML::Functions.boolean(1.1))
+    end
+
+    def test_float_positive_zero
+      assert_equal(false, REXML::Functions.boolean(-0.0))
+    end
+
+    def test_float_negative_zero
+      assert_equal(false, REXML::Functions.boolean(-0.0))
+    end
+
+    def test_float_nan
+      assert_equal(false, REXML::Functions.boolean(Float::NAN))
+    end
+
+    def test_string_true
+      assert_equal(true, REXML::Functions.boolean("content"))
+    end
+
+    def test_string_empty
+      assert_equal(false, REXML::Functions.boolean(""))
+    end
+
+    def test_node_set_true
+      root = REXML::Document.new("<root/>").root
+      assert_equal(true, REXML::Functions.boolean([root]))
+    end
+
+    def test_node_set_empty
+      assert_equal(false, REXML::Functions.boolean([]))
+    end
+
+    def test_nil
+      assert_equal(false, REXML::Functions.boolean(nil))
+    end
+
+    def test_context
+      REXML::Functions.context = {node: true}
+      assert_equal(true, REXML::Functions.boolean())
+    end
+  end
+end