Range of fixed-length integer generators differs from documentation

[szktty]

Description

The range of integers generated by fixed-length integer generators does not match the documentation, or an assertion error occurs. For example, any.uint8 is supposed to generate integers ranging from 0 to 255 inclusive, but in reality, it generates integers ranging from 0 to 511 inclusive.

The affected generators include:

• any.uint8
• any.uint16
• any.uint32
• any.int8
• any.int16
• any.int32
• any.int64 (causes an assertion error)

Environment

• macOS 14.2.1
• Dart 3.2.6
• Glados 1.1.7

Current behavior

• any.uint8 generates integers from 0 (inclusive) to 512 (exclusive).
• any.uint16 generates integers from 0 (inclusive) to 131072 (exclusive).
• any.uint32 generates integers from 0 (inclusive) to 8589934592 (exclusive).
• any.int8 generates integers from -256 (inclusive) to 256 (exclusive).
• any.int16 generates integers from -65536 (inclusive) to 65536 (exclusive).
• any.int32 generates integers from -4294967296 (inclusive) to 4294967296 (exclusive).
• any.int64 is causing an assertion error.

The assertion error caused by using any.int64 is as follows:

00:00 +0 -1: loading test/glados_report_test.dart [E]                       
  Failed to load "test/glados_report_test.dart": 'package:glados/src/anys.dart': Failed assertion: line 27 pos 44: 'min < max': is not true.
  dart:core                           _AssertionError._throwNew
  package:glados/src/anys.dart 27:44  IntAnys.intInRange
  package:glados/src/anys.dart 81:36  IntAnys.int64
  test/glados_report_test.dart 30:14  main

Expected behavior

The range of integers generated by the generators matches the documentation.

• any.uint8 generates integers from 0 (inclusive) to 256 (exclusive).
• any.uint16 generates integers from 0 (inclusive) to 65536 (exclusive).
• any.uint32 generates integers from 0 (inclusive) to 4294967296 (exclusive).
• any.int8 generates integers from -128 (inclusive) to 128 (exclusive).
• any.int16 generates integers from -32768 (inclusive) to 32768 (exclusive).
• any.int32 generates integers from -2147483648 (inclusive) to 2147483648 (exclusive).
• any.int64 generates integers from -9223372036854775808 (inclusive) to 9223372036854775808 (exclusive).

The current implementation uses a bit shift of 2 where it should use a bit shift of 1. The assertion error when using any.int64 occurs because the specified minimum value -(2 << 63) and the maximum value 2 << 63 both result in 0. Changing from a bit shift of 2 to a bit shift of 1 should fix the issue.

The current implementation is as follows:

https://github.com/MarcelGarus/glados/blob/d86f83ba0701bbed7ec39090f18e737a5893d305/glados/lib/src/anys.dart#L56C1-L81C68

/// A generator that returns [int]s between `0`, inclusive, to `256`, exclusive.
Generator<core.int> get uint8 => intInRange(0, 2 << 8);

/// A generator that returns [int]s between `0`, inclusive, to `65536`,
/// exclusive.
Generator<core.int> get uint16 => intInRange(0, 2 << 16);

/// A generator that returns [int]s between `0`, inclusive, to `4294967296`,
/// exclusive.
Generator<core.int> get uint32 => intInRange(0, 2 << 32);

/// A generator that returns [int]s between `-128`, inclusive, to `128`,
/// exclusive.
Generator<core.int> get int8 => intInRange(-(2 << 7), 2 << 7);

/// A generator that returns [int]s between `-32768`, inclusive, to `32768`,
/// exclusive.
Generator<core.int> get int16 => intInRange(-(2 << 15), 2 << 15);

/// A generator that returns [int]s between `-2147483648`, inclusive, to
/// `2147483648`, exclusive.
Generator<core.int> get int32 => intInRange(-(2 << 31), 2 << 31);

/// A generator that returns [int]s between `-9223372036854775808`, inclusive,
/// to `9223372036854775808`, exclusive.
Generator<core.int> get int64 => intInRange(-(2 << 63), 2 << 63);

The tests are also implemented using the same bit shift expressions, so the tests need to be corrected as well.

glados/glados/test/anys_test.dart

Line 39 in d86f83b

Glados(any.uint8).test('uint8', (number) {

Glados(any.uint8).test('uint8', (number) {
  expect(number, greaterThanOrEqualTo(0));
  expect(number, lessThan(2 << 8));
});
Glados(any.uint16).test('uint16', (number) {
  expect(number, greaterThanOrEqualTo(0));
  expect(number, lessThan(2 << 16));
});
Glados(any.uint32).test('uint32', (number) {
  expect(number, greaterThanOrEqualTo(0));
  expect(number, lessThan(2 << 32));
});

Steps to reproduce

Unit tests verifying the range of integers generated by the generators are shown below.

import 'package:glados/glados.dart';

void main() {
  Glados(any.uint8).test('uint8: 0 to 255', (value) {
    expect(0 <= value && value <= 255, true);
  });

  Glados(any.uint16).test('uint16: 0 to 65535', (value) {
    expect(0 <= value && value <= 65535, true);
  });

  Glados(any.uint32).test('uint32: 0 to 4294967294', (value) {
    expect(0 <= value && value <= 4294967295, true);
  });

  Glados(any.int8).test('int8: -128 to 127', (value) {
    expect(-128 <= value && value <= 127, true);
  });

  Glados(any.int16).test('int16: -32768 to 32767', (value) {
    expect(-32768 <= value && value <= 32767, true);
  });

  Glados(any.int32).test('int32: -2147483648 to 2147483647', (value) {
    expect(-2147483648 <= value && value <= 2147483647, true);
  });

  // This code will fail due to an assertion error
  /*
  Glados(any.int64).test('int64: -9223372036854775808 to 9223372036854775807',
      (value) {
    expect(-9223372036854775808 <= value && value <= 9223372036854775807, true);
  });
  */
}

The test results are as follows:

% dart test --no-fail-fast
00:00 +0: loading test/glados_report_test.dart                              
intInRange(0, 0);
00:00 +0: test/glados_report_test.dart: uint8: 0 to 255 (testing 100 inputs)
Tested 2 inputs, shrunk 175 times.
Failing for input: 256
00:00 +0 -1: test/glados_report_test.dart: uint8: 0 to 255 (testing 100 inputs) [E]
  Expected: <true>
    Actual: <false>
  
  package:matcher                        expect
  test/glados_report_test.dart 7:5       main.<fn>
  package:glados/src/glados.dart 178:28  Glados.test.<fn>
  

To run this test again: dart test test/glados_report_test.dart -p vm --plain-name 'uint8: 0 to 255 (testing 100 inputs)'
00:00 +0 -1: test/glados_report_test.dart: uint16: 0 to 65535 (testing 100 inputs)
Tested 2 inputs, shrunk 58799 times.
Failing for input: 65536
00:00 +0 -2: test/glados_report_test.dart: uint16: 0 to 65535 (testing 100 inputs) [E]
  Expected: <true>
    Actual: <false>
  
  package:matcher                        expect
  test/glados_report_test.dart 11:5      main.<fn>
  package:glados/src/glados.dart 178:28  Glados.test.<fn>
  

To run this test again: dart test test/glados_report_test.dart -p vm --plain-name 'uint16: 0 to 65535 (testing 100 inputs)'
00:00 +1 -2: test/glados_report_test.dart: int8: -128 to 127 (testing 100 inputs)
Tested 1 input, shrunk 77 times.
Failing for input: -129
00:00 +1 -3: test/glados_report_test.dart: int8: -128 to 127 (testing 100 inputs) [E]
  Expected: <true>
    Actual: <false>
  
  package:matcher                        expect
  test/glados_report_test.dart 19:5      main.<fn>
  package:glados/src/glados.dart 178:28  Glados.test.<fn>
  

To run this test again: dart test test/glados_report_test.dart -p vm --plain-name 'int8: -128 to 127 (testing 100 inputs)'
00:00 +1 -3: test/glados_report_test.dart: int16: -32768 to 32767 (testing 100 inputs)
Tested 2 inputs, shrunk 26031 times.
Failing for input: 32768
00:00 +1 -4: test/glados_report_test.dart: int16: -32768 to 32767 (testing 100 inputs) [E]
  Expected: <true>
    Actual: <false>
  
  package:matcher                        expect
  test/glados_report_test.dart 23:5      main.<fn>
  package:glados/src/glados.dart 178:28  Glados.test.<fn>
  

To run this test again: dart test test/glados_report_test.dart -p vm --plain-name 'int16: -32768 to 32767 (testing 100 inputs)'
00:08 +1 -4: ... int32: -2147483648 to 2147483647 (testing 100 inputs)      
63:09 +1 -4: test/glados_report_test.dart: int32: -2147483648 to 2147483647 (testing 100 inputs)
Tested 1 input, shrunk 2147483648 times.
Failing for input: -2147483649
63:09 +1 -5: test/glados_report_test.dart: int32: -2147483648 to 2147483647 (testing 100 inputs) [E]
  Expected: <true>
    Actual: <false>
  
  package:matcher                        expect
  test/glados_report_test.dart 27:5      main.<fn>
  package:glados/src/glados.dart 178:28  Glados.test.<fn>
  

To run this test again: dart test test/glados_report_test.dart -p vm --plain-name 'int32: -2147483648 to 2147483647 (testing 100 inputs)'
63:09 +1 -5: Some tests failed.