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assert_matches costs ~38x a string comparison, undocumented #1187

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assert_matches costs ~38x a string comparison, undocumented#1187
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opened on Aug 13, 2026

Measured

assertioncountwallper call
assert_same2000~130 ms0.065 ms
assert_contains2000~180 ms0.09 ms
assert_matches500~1.25 s2.5 ms (~38x)

Stable across three runs each.

Why, and why it is not a bug

assert_matches forks grep -E per call. .claude/rules/perf-fork-budget.md
already records the reason — Bash 3.2 changed whether a quoted right-hand side
of [[ =~ ]] is a regex or a literal, so at the Bash 3.0 floor the same pattern
would match differently across supported versions, and removing the fork means
picking one semantic and breaking the other.

Not proposing to change it. That trade is decided, and the rule says not to
chase it.

What is missing

The cost was never quantified anywhere, and users have no way to know. A suite
asserting inside a large loop pays 38x without a hint that a cheaper assertion
would do.

  • Quantify it in the internal rule, so the trade is weighable rather than just
    asserted.
  • Note it in docs/assertions.md, pointing at assert_contains when the
    pattern is a fixed substring.

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assert_matches costs ~38x a string comparison, undocumented · Issue #1187 · TypedDevs/bashunit · GitHub
Skip to content
assert_matches costs ~38x a string comparison, undocumented #1187
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assert_matches costs ~38x a string comparison, undocumented#1187
Assignees
Chemaclass
Labels
documentationImprovements or additions to documentation
Description
@Chemaclass
Chemaclass
opened on Aug 13, 2026
Measured
assertioncountwallper call
assert_same2000~130 ms0.065 ms
assert_contains2000~180 ms0.09 ms
assert_matches500~1.25 s2.5 ms (~38x)
Stable across three runs each.
Why, and why it is not a bug
assert_matches forks grep -E per call. .claude/rules/perf-fork-budget.md

already records the reason — Bash 3.2 changed whether a quoted right-hand side

of [[ =~ ]] is a regex or a literal, so at the Bash 3.0 floor the same pattern

would match differently across supported versions, and removing the fork means

picking one semantic and breaking the other.
Not proposing to change it. That trade is decided, and the rule says not to

chase it.
What is missing
The cost was never quantified anywhere, and users have no way to know. A suite

asserting inside a large loop pays 38x without a hint that a cheaper assertion

would do.
  • Quantify it in the internal rule, so the trade is weighable rather than just
    
asserted.
  • Note it in docs/assertions.md, pointing at assert_contains when the
    
pattern is a fixed substring.
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var __m = "*";
var __re = new RegExp('^' + ".*" + '
assert_matches costs ~38x a string comparison, undocumented · Issue #1187 · TypedDevs/bashunit · GitHub
Skip to content
assert_matches costs ~38x a string comparison, undocumented #1187
Closed
Closed
assert_matches costs ~38x a string comparison, undocumented#1187
Assignees
Chemaclass
Labels
documentationImprovements or additions to documentation
Description
@Chemaclass
Chemaclass
opened on Aug 13, 2026
Measured
assertioncountwallper call
assert_same2000~130 ms0.065 ms
assert_contains2000~180 ms0.09 ms
assert_matches500~1.25 s2.5 ms (~38x)
Stable across three runs each.
Why, and why it is not a bug
assert_matches forks grep -E per call. .claude/rules/perf-fork-budget.md

already records the reason — Bash 3.2 changed whether a quoted right-hand side

of [[ =~ ]] is a regex or a literal, so at the Bash 3.0 floor the same pattern

would match differently across supported versions, and removing the fork means

picking one semantic and breaking the other.
Not proposing to change it. That trade is decided, and the rule says not to

chase it.
What is missing
The cost was never quantified anywhere, and users have no way to know. A suite

asserting inside a large loop pays 38x without a hint that a cheaper assertion

would do.
  • Quantify it in the internal rule, so the trade is weighable rather than just
    
asserted.
  • Note it in docs/assertions.md, pointing at assert_contains when the
    
pattern is a fixed substring.
Metadata
Metadata
Assignees
Labels
documentationImprovements or additions to documentation
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Projects
  • bashunit
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Issue actions

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(function(){
try {
var __m = "*";
var __re = new RegExp('^' + ".*" + '
assert_matches costs ~38x a string comparison, undocumented · Issue #1187 · TypedDevs/bashunit · GitHub
Skip to content
assert_matches costs ~38x a string comparison, undocumented #1187
Closed
Closed
assert_matches costs ~38x a string comparison, undocumented#1187
Assignees
Chemaclass
Labels
documentationImprovements or additions to documentation
Description
@Chemaclass
Chemaclass
opened on Aug 13, 2026
Measured
assertioncountwallper call
assert_same2000~130 ms0.065 ms
assert_contains2000~180 ms0.09 ms
assert_matches500~1.25 s2.5 ms (~38x)
Stable across three runs each.
Why, and why it is not a bug
assert_matches forks grep -E per call. .claude/rules/perf-fork-budget.md

already records the reason — Bash 3.2 changed whether a quoted right-hand side

of [[ =~ ]] is a regex or a literal, so at the Bash 3.0 floor the same pattern

would match differently across supported versions, and removing the fork means

picking one semantic and breaking the other.
Not proposing to change it. That trade is decided, and the rule says not to

chase it.
What is missing
The cost was never quantified anywhere, and users have no way to know. A suite

asserting inside a large loop pays 38x without a hint that a cheaper assertion

would do.
  • Quantify it in the internal rule, so the trade is weighable rather than just
    
asserted.
  • Note it in docs/assertions.md, pointing at assert_contains when the
    
pattern is a fixed substring.
Metadata
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try {
var __m = "youtube.com";
var __re = new RegExp('^' + "youtube\\.com" + '
assert_matches costs ~38x a string comparison, undocumented · Issue #1187 · TypedDevs/bashunit · GitHub
Skip to content
assert_matches costs ~38x a string comparison, undocumented #1187
Closed
Closed
assert_matches costs ~38x a string comparison, undocumented#1187
Assignees
Chemaclass
Labels
documentationImprovements or additions to documentation
Description
@Chemaclass
Chemaclass
opened on Aug 13, 2026
Measured
assertioncountwallper call
assert_same2000~130 ms0.065 ms
assert_contains2000~180 ms0.09 ms
assert_matches500~1.25 s2.5 ms (~38x)
Stable across three runs each.
Why, and why it is not a bug
assert_matches forks grep -E per call. .claude/rules/perf-fork-budget.md

already records the reason — Bash 3.2 changed whether a quoted right-hand side

of [[ =~ ]] is a regex or a literal, so at the Bash 3.0 floor the same pattern

would match differently across supported versions, and removing the fork means

picking one semantic and breaking the other.
Not proposing to change it. That trade is decided, and the rule says not to

chase it.
What is missing
The cost was never quantified anywhere, and users have no way to know. A suite

asserting inside a large loop pays 38x without a hint that a cheaper assertion

would do.
  • Quantify it in the internal rule, so the trade is weighable rather than just
    
asserted.
  • Note it in docs/assertions.md, pointing at assert_contains when the
    
pattern is a fixed substring.
Metadata
Metadata
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documentationImprovements or additions to documentation
Type
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Projects
  • bashunit
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, 'i');
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(function(){
try {
var __m = "*";
var __re = new RegExp('^' + ".*" + '
assert_matches costs ~38x a string comparison, undocumented · Issue #1187 · TypedDevs/bashunit · GitHub
Skip to content
assert_matches costs ~38x a string comparison, undocumented #1187
Closed
Closed
assert_matches costs ~38x a string comparison, undocumented#1187
Assignees
Chemaclass
Labels
documentationImprovements or additions to documentation
Description
@Chemaclass
Chemaclass
opened on Aug 13, 2026
Measured
assertioncountwallper call
assert_same2000~130 ms0.065 ms
assert_contains2000~180 ms0.09 ms
assert_matches500~1.25 s2.5 ms (~38x)
Stable across three runs each.
Why, and why it is not a bug
assert_matches forks grep -E per call. .claude/rules/perf-fork-budget.md

already records the reason — Bash 3.2 changed whether a quoted right-hand side

of [[ =~ ]] is a regex or a literal, so at the Bash 3.0 floor the same pattern

would match differently across supported versions, and removing the fork means

picking one semantic and breaking the other.
Not proposing to change it. That trade is decided, and the rule says not to

chase it.
What is missing
The cost was never quantified anywhere, and users have no way to know. A suite

asserting inside a large loop pays 38x without a hint that a cheaper assertion

would do.
  • Quantify it in the internal rule, so the trade is weighable rather than just
    
asserted.
  • Note it in docs/assertions.md, pointing at assert_contains when the
    
pattern is a fixed substring.
Metadata
Metadata
Assignees
Labels
documentationImprovements or additions to documentation
Type
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Projects
  • bashunit
    Status
    Done
Milestone
No milestone
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Issue actions

, 'i');
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(function(){
try {
var __m = "*";
var __re = new RegExp('^' + ".*" + '
assert_matches costs ~38x a string comparison, undocumented · Issue #1187 · TypedDevs/bashunit · GitHub
Skip to content
assert_matches costs ~38x a string comparison, undocumented #1187
Closed
Closed
assert_matches costs ~38x a string comparison, undocumented#1187
Assignees
Chemaclass
Labels
documentationImprovements or additions to documentation
Description
@Chemaclass
Chemaclass
opened on Aug 13, 2026
Measured
assertioncountwallper call
assert_same2000~130 ms0.065 ms
assert_contains2000~180 ms0.09 ms
assert_matches500~1.25 s2.5 ms (~38x)
Stable across three runs each.
Why, and why it is not a bug
assert_matches forks grep -E per call. .claude/rules/perf-fork-budget.md

already records the reason — Bash 3.2 changed whether a quoted right-hand side

of [[ =~ ]] is a regex or a literal, so at the Bash 3.0 floor the same pattern

would match differently across supported versions, and removing the fork means

picking one semantic and breaking the other.
Not proposing to change it. That trade is decided, and the rule says not to

chase it.
What is missing
The cost was never quantified anywhere, and users have no way to know. A suite

asserting inside a large loop pays 38x without a hint that a cheaper assertion

would do.
  • Quantify it in the internal rule, so the trade is weighable rather than just
    
asserted.
  • Note it in docs/assertions.md, pointing at assert_contains when the
    
pattern is a fixed substring.
Metadata
Metadata
Assignees
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documentationImprovements or additions to documentation
Type
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Projects
  • bashunit
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, 'i');
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var enabled = true;
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})();
assert_matches costs ~38x a string comparison, undocumented · Issue #1187 · TypedDevs/bashunit · GitHub
Skip to content
assert_matches costs ~38x a string comparison, undocumented #1187
Closed
Closed
assert_matches costs ~38x a string comparison, undocumented#1187
Assignees
Chemaclass
Labels
documentationImprovements or additions to documentation
Description
@Chemaclass
Chemaclass
opened on Aug 13, 2026
Measured
assertioncountwallper call
assert_same2000~130 ms0.065 ms
assert_contains2000~180 ms0.09 ms
assert_matches500~1.25 s2.5 ms (~38x)
Stable across three runs each.
Why, and why it is not a bug
assert_matches forks grep -E per call. .claude/rules/perf-fork-budget.md

already records the reason — Bash 3.2 changed whether a quoted right-hand side

of [[ =~ ]] is a regex or a literal, so at the Bash 3.0 floor the same pattern

would match differently across supported versions, and removing the fork means

picking one semantic and breaking the other.
Not proposing to change it. That trade is decided, and the rule says not to

chase it.
What is missing
The cost was never quantified anywhere, and users have no way to know. A suite

asserting inside a large loop pays 38x without a hint that a cheaper assertion

would do.
  • Quantify it in the internal rule, so the trade is weighable rather than just
    
asserted.
  • Note it in docs/assertions.md, pointing at assert_contains when the
    
pattern is a fixed substring.
Metadata
Metadata
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documentationImprovements or additions to documentation
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Projects
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