A few more test and some code fiddling

R/regex.R

         result_pad <- sprintf("pad%02d", max_pad_level - 3)
       }
     }
-    paste("<p class='results", result_pad, "'>", resi, "</p>")
+    paste('<p class="results', result_pad, '">', resi, "</p>")
   })
   res <- paste(res, collapse = "")
   if (!nchar(pattern)) res <- paste("<p class='results'>", text, "</p>")
   tmp_html <- suppressWarnings(
     rmarkdown::render(
       tmp,
-      output_format = rmarkdown::html_document(css = c(system.file("styles", 'skeleton.css', package='regexplain'),
-                                                       system.file("styles", 'view_regex.css', package='regexplain'),
-                                                       system.file("styles", 'groups.css', package='regexplain')),
-                                               theme = NULL,
-                                               md_extensions = "-autolink_bare_uris"),
+      output_format = rmarkdown::html_document(
+        css = c(system.file("styles", 'skeleton.css', package='regexplain'),
+                system.file("styles", 'view_regex.css', package='regexplain'),
+                system.file("styles", 'groups.css', package='regexplain')),
+        theme = NULL,
+        md_extensions = "-autolink_bare_uris"),
       quiet = TRUE
   ))
   rstudioapi::viewer(tmp_html)

tests/testthat/test-regex.R

   m <- regex(text, pattern, global = TRUE)
   expect_equal(unique(m[[1]]$idx$pass), c(1L, 2L))
 })
+
+test_that("view_regex generall works", {
+  result <- "<p class=\"results  \"> <span class=\"group g00\"><span class=\"group g01\">t</span>e</span><span class=\"group g00\"><span class=\"group g01\">s</span>t</span> </p>"
+  expect_equal(view_regex("test", "(\\w)\\w", render = FALSE), result)
+})

tests/testthat/test-wrap_regex.R

   expect_equal(wrap_regex("((?:a(b))c)"),
                "<span class=\"g01\">((?:a<span class=\"g02\">(b)</span>)c)</span>")
 })
+
+test_that("wrap_regex returns text if no matches", {
+  expect_equal(
+    wrap_result(list(text = "no result")),
+    "no result"
+  )
+})

tests/testthat/test-wrap_result.R

   )
   expect_equal(wrap_result(regex(text, pattern, global = TRUE)[[1]]), result)
 })
+
+test_that("handles escaped parentheses", {
+  expect_equal(
+    wrap_regex("\\((word)\\)"),
+    '\\\\(<span class=\"g01\">(word)</span>\\\\)'
+  )
+})
+
+test_that("wrap_result with exact = TRUE", {
+  # input/output standard R characters
+  expect_equal(
+    wrap_result(regex("a\\b", "\\\\")[[1]]),
+    "a<span class=\"group g00\">\\</span>b"
+  )
+
+  # input is "literal", output is R string to match literal input
+  expect_equal(
+    wrap_result(regex("a\\b", "\\\\")[[1]], exact = TRUE),
+    "a<span class=\"group g00\">\\\\</span>b"
+  )
+})