Implement ReaderAssert in a similar way as InputStreamAssert

[assertj]

Implement ReaderAssert in a similar way as InputStreamAssert

[joel-costigliola]

We decided to close it since it was a bit of a corner case considering that there are ways to obtain an InputStream from a Reader and we have InputStream assertions.

[nach-o-man]

If it is still desired I could try implementing it.

[joel-costigliola]

@nach-o-man thanks for your interest, I'll discuss with the team to see if it is still relevant (quite an old issue 😅 )

[nach-o-man]

Indeed it is. Will browse to check if there is anythin I could grab. :)

[davidsusu]

ReaderAssert would be very useful. IMO Reader and InputStream are quite different. From a testing perspective Reader (with a small content) is more like to String.

InputStreamAssert could have asReader(Charset). (Also, InputStreamAssert should have an asString(Charset) method, just like ByteArrayAssert.)

there are ways to obtain an InputStream from a Reader

What do you mean by this? In some cases, it's not so easy. The standard library has no tool for generally achieving such a conversion (of course, apache-commons has ReaderInputStream, like some other third-party helper libs). Either way, ReaderAssert would be the proper fluent way to test Readers.

[scordio]

@davidsusu would you have some concrete examples to help re-evaluate the topic?

[davidsusu]

@scordio As a very basic example, this test:

assertThat(IOUtils.toString(clob.getCharacterStream())).isEqualTo("abcdefghi");

could be:

assertThat(clob.getCharacterStream()).hasContent("abcdefghi");

The latter is cleaner and shorter while requires no extra library or helper method.

Other lifelike examples:

assertThat(myReader).contains("some substring");
assertThat(myInputStream).asReader(StandardCharsets.UTF_8).contains("some substring");
assertThat(myReader).containsOnlyDigits();
assertThat(myReader).hasSize(42_424_242);
assertThat(myReader).hasSizeGreaterThan(343);
assertThat(myReader).hasSameContentAs(referenceReader);
assertThat(myReader).hasSameContentAsIgnoringWhitespace(referenceReader);
assertThat(myReader).hasSameSizeAs(referenceReader);
assertThat(myReader).decodedAsBase64().hasSameContentAs(referenceInputStream);
assertThat(myReader).decodedAsBase64().hasSameContentAs(referenceInputStream);
assertThat(myReader).decodedAsBase64(StandardCharsets.UTF_8).hasSameContentAs(referenceReader);
assertThat(myReader).asCharacterIterable().doesNotContain('x', 'y');

In these cases we handle the Reader nearly as simple as a String, but without the overhead of loading the entire content into the memory.