Add additional formula cell types: Date, TrueClass, FalseClass

lib/roo/base.rb

@@ -726,7 +726,7 @@ def cell_to_csv(row, col, sheet)
         else
           onecell.to_s
         end
-      when DateTime
+      when Date, DateTime, TrueClass, FalseClass
         onecell.to_s
       else
         fail "unhandled onecell-class #{onecell.class}"

test/excelx/test_formula_to_csv.rb

@@ -0,0 +1,21 @@
+require 'test_helper'
+
+class TestRooFormulaToCsv < Minitest::Test
+  def cell_to_csv(row, col)
+    Roo::Spreadsheet.open(
+      File.join(TESTDIR, 'formula_cell_types.xlsx')
+    ).send('cell_to_csv', row, col, 'Sheet1')
+  end
+
+  def test_true_class
+    assert_equal 'true', cell_to_csv(1, 1)
+  end
+
+  def test_false_class
+    assert_equal 'false', cell_to_csv(2, 1)
+  end
+
+  def test_date_class
+    assert_equal '2017-01-01', cell_to_csv(3, 1)
+  end
+end