System in can use less home-made code #16
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ashleyfrieze
commented
Nov 13, 2020
ashleyfrieze
commented
- Surprising behaviour with Scanner suggests home-made code acted unusually
- Surprising behaviour with Scanner suggests home-made code acted unusually
| @@ -220,7 +220,7 @@ void Scanner_reads_text_from_System_in( | |||
| withTextFromSystemIn("first line", "second line") | |||
| .execute(() -> { | |||
| Scanner scanner = new Scanner(System.in); | |||
| scanner.nextLine(); | |||
| assertEquals("first line", scanner.nextLine()); | |||
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Increase clarity of the second assert
| AtomicReference<String> secondLineCapture = new AtomicReference<>(); | ||
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| withTextFromSystemIn( | ||
| "first line", | ||
| "second line" | ||
| ).execute(() -> { | ||
| Scanner firstScanner = new Scanner(in); | ||
| firstScanner.nextLine(); | ||
| Scanner secondScanner = new Scanner(in); |
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The first scanner may cache more than just the first line, so the second scanner is unable to pick up the second line.
| ) throws Exception { | ||
| withTextFromSystemIn() | ||
| .andExceptionThrownOnInputEnd(DUMMY_IO_EXCEPTION) | ||
| .execute(() -> { | ||
| int numBytesRead = System.in.read(DUMMY_ARRAY, VALID_OFFSET, 0); | ||
| assertThat(numBytesRead).isZero(); | ||
| assertThat(numBytesRead).isEqualTo(-1); |
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read should return -1 at the end of the stream.
- Surprising behaviour with Scanner suggests home-made code acted unusually - Interface for `read` was broken - should return `-1` at stream end
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I've encountered some surprises with this implementation. I think the home made stream was there to solve a problem that was not covered by the original unit tests for SystemLambda. I've put the missing tests into #18 I'd like a little clarification, please. What's the intended behaviour? Some of the tests in #18 will likely fail if we use more conventional implementations of |
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Further review suggests that this is not a viable solution... worth exploring whether the behaviour in #18 is what's expected. |
