Move processing of reveal_options out of main format (#126)

This includes the addition of unit tests
diff --git a/tests/testthat/test-utils.R b/tests/testthat/test-utils.R
new file mode 100644
index 0000000..c53a50d
--- /dev/null
+++ b/tests/testthat/test-utils.R
@@ -0,0 +1,29 @@
+test_that("reveal options are passed as pandoc variables", {
+  expect_equal(process_reveal_option("a", "b"), pandoc_variable_arg("a", "b"))
+})
+
+test_that("reveal options with boolean are transformed to JS bool", {
+  expect_equal(process_reveal_option("a", TRUE), pandoc_variable_arg("a", "true"))
+  expect_equal(process_reveal_option("a", FALSE), pandoc_variable_arg("a", "false"))
+})
+
+test_that("reveal options slideNumbers is treated specifically", {
+  expect_equal(process_reveal_option("slideNumber", "c/t"), pandoc_variable_arg("slideNumber", "'c/t'"))
+  expect_equal(process_reveal_option("slideNumber", TRUE), pandoc_variable_arg("slideNumber", "true"))
+})
+
+test_that("reveal options width / heigh in % are quoted", {
+  expect_equal(process_reveal_option("width", "50%"), pandoc_variable_arg("width", "'50%'"))
+  expect_equal(process_reveal_option("height", "50%"), pandoc_variable_arg("height", "'50%'"))
+  expect_equal(process_reveal_option("width", 5), pandoc_variable_arg("width", "5"))
+  expect_equal(process_reveal_option("height", 5), pandoc_variable_arg("height", "5"))
+})
+
+test_that("reveal options for chalkboard plugins special handling", {
+  expect_equal(process_reveal_option("chalkboard-background", "rgba(255,255,255,0.5)"), pandoc_variable_arg("chalkboard-background", "['rgba(255,255,255,0.5)']"))
+  expect_equal(process_reveal_option("chalkboard-color", c("a", "b")), pandoc_variable_arg("chalkboard-color", "['a', 'b']"))
+  expect_equal(process_reveal_option("chalkboard-draw", c("a", "b")), pandoc_variable_arg("chalkboard-draw", "['a', 'b']"))
+  expect_equal(process_reveal_option("chalkboard-pen", c("a", "b")), pandoc_variable_arg("chalkboard-pen", "['a', 'b']"))
+  expect_equal(process_reveal_option("chalkboard-other", "dummy"), pandoc_variable_arg("chalkboard-other", "dummy"))
+})
+