Better expect_output checks for NA and NULL.

Fixes #323.

NEWS.md

@@ -1,5 +1,11 @@
 # testthat 0.11.0.9000
 
+* `expect_output(f(), NA)` will fail if `f()` produces output; 
+  `expect_output(f(), NULL)` will fail if `f()` doesn't produce output (#323).
+
+* `expect_output()` no longer prints the output by default. You need to do this
+  yourself.
+
 * `expect_type()` checks the _type_ of the object (#316).
 
 * `not()` has been deprecated.

R/expectations-matches.R

@@ -94,7 +94,7 @@ matches <- function(regexp, all = TRUE, ...) {
 
 #' @export
 #' @rdname matching-expectations
-expect_output <- function(object, regexp, ..., info = NULL, label = NULL) {
+expect_output <- function(object, regexp = NULL, ..., info = NULL, label = NULL) {
   if (is.null(label)) {
     label <- find_expr("object")
   }
@@ -104,17 +104,23 @@ expect_output <- function(object, regexp, ..., info = NULL, label = NULL) {
 #' @rdname oldskool
 prints_text <- function(regexp, ...) {
   function(expr) {
-    output <- evaluate_promise(expr, print = TRUE)$output
+    output <- evaluate_promise(expr)$output
 
     if (identical(regexp, NA)) {
-      return(expectation(
-        !is.null(output),
+      expectation(
+        identical(output, ""),
         paste0("produced output: ", encodeString(output)),
         "didn't produce output"
-      ))
+      )
+    } else if (is.null(regexp)) {
+      expectation(
+        !identical(output, ""),
+        "didn't produce output",
+        "produced output"
+      )
+    } else {
+      matches(regexp, ...)(output)
     }
-
-    matches(regexp, ...)(output)
   }
 }
 

R/test-that.r

@@ -32,6 +32,7 @@ test_that <- function(desc, code) {
 }
 
 
+
 # Executes a test.
 #
 # @keywords internal

tests/testthat/test-expectations.r

@@ -79,10 +79,6 @@ test_that("expect_output captures multiline code", {
   expect_output(cat("1\n2"), "1\n2")
 })
 
-test_that("expect_output prints by default", {
-  expect_output(1, "1")
-})
-
 test_that("expect_equals fails with useful message if objects equal but not identical", {
   f <- function() x
   g <- function() x