fix: add explicit error message for null or undefined matchers (#718)

* Added explicit error message for null or undefined matchers

* Updated message

* Whoops, no quotes

Author: Josh Goldberg

src/__tests__/matches.js

@@ -26,3 +26,16 @@ test('matchers return false if text to match is not a string', () => {
   expect(matches(null, node, 'ABC', normalizer)).toBe(false)
   expect(fuzzyMatches(null, node, 'ABC', normalizer)).toBe(false)
 })
+
+test('matchers throw on invalid matcher inputs', () => {
+  expect(() =>
+    matches('ABC', node, null, normalizer),
+  ).toThrowErrorMatchingInlineSnapshot(
+    `"It looks like null was passed instead of a matcher. Did you do something like getByText(null)?"`,
+  )
+  expect(() =>
+    fuzzyMatches('ABC', node, undefined, normalizer),
+  ).toThrowErrorMatchingInlineSnapshot(
+    `"It looks like undefined was passed instead of a matcher. Did you do something like getByText(undefined)?"`,
+  )
+})

src/matches.js

@@ -1,8 +1,18 @@
+function assertNotNullOrUndefined(matcher) {
+  if (matcher == null) {
+    throw new Error(
+      `It looks like ${matcher} was passed instead of a matcher. Did you do something like getByText(${matcher})?`,
+    )
+  }
+}
+
 function fuzzyMatches(textToMatch, node, matcher, normalizer) {
   if (typeof textToMatch !== 'string') {
     return false
   }
 
+  assertNotNullOrUndefined(matcher)
+
   const normalizedText = normalizer(textToMatch)
   if (typeof matcher === 'string') {
     return normalizedText.toLowerCase().includes(matcher.toLowerCase())
@@ -18,6 +28,8 @@ function matches(textToMatch, node, matcher, normalizer) {
     return false
   }
 
+  assertNotNullOrUndefined(matcher)
+
   const normalizedText = normalizer(textToMatch)
   if (typeof matcher === 'string') {
     return normalizedText === matcher