Add tests for _dd.p.ksr rounding at 6-decimal boundary

bm1549 · claude · bm1549 · commit 67b831221a1b · 2026-03-25T11:10:37.000-04:00
Test three boundary cases for small sampling rates:
- 0.00000051 rounds up to 0.000001
- 0.000001 stays exactly 0.000001
- 0.0000001 rounds down to 0

Co-Authored-By: Claude Opus 4.6 (1M context) &lt;noreply@anthropic.com&gt;
diff --git a/tests/ext/priority_sampling/030-ksr-tag-rounding-boundary.phpt b/tests/ext/priority_sampling/030-ksr-tag-rounding-boundary.phpt
@@ -0,0 +1,19 @@
+--TEST--
+_dd.p.ksr rounds small rates correctly at 6-decimal boundary
+--ENV--
+DD_TRACE_SAMPLING_RULES=[{"sample_rate": 0.00000051}]
+DD_TRACE_GENERATE_ROOT_SPAN=1
+--FILE--
+<?php
+$root = \DDTrace\root_span();
+
+\DDTrace\get_priority_sampling();
+
+$ksr = isset($root->meta["_dd.p.ksr"]) ? $root->meta["_dd.p.ksr"] : "-";
+echo "_dd.p.ksr = ", $ksr, "\n";
+// 0.00000051 rounds up to 0.000001 at 6 decimal places
+echo "no_sci_notation = ", (strpos($ksr, 'e') === false) ? "true" : "false", "\n";
+?>
+--EXPECT--
+_dd.p.ksr = 0.000001
+no_sci_notation = true
diff --git a/tests/ext/priority_sampling/031-ksr-tag-exact-sixth-decimal.phpt b/tests/ext/priority_sampling/031-ksr-tag-exact-sixth-decimal.phpt
@@ -0,0 +1,18 @@
+--TEST--
+_dd.p.ksr preserves exact 0.000001 rate without rounding away
+--ENV--
+DD_TRACE_SAMPLING_RULES=[{"sample_rate": 0.000001}]
+DD_TRACE_GENERATE_ROOT_SPAN=1
+--FILE--
+<?php
+$root = \DDTrace\root_span();
+
+\DDTrace\get_priority_sampling();
+
+$ksr = isset($root->meta["_dd.p.ksr"]) ? $root->meta["_dd.p.ksr"] : "-";
+echo "_dd.p.ksr = ", $ksr, "\n";
+echo "no_sci_notation = ", (strpos($ksr, 'e') === false) ? "true" : "false", "\n";
+?>
+--EXPECT--
+_dd.p.ksr = 0.000001
+no_sci_notation = true
diff --git a/tests/ext/priority_sampling/032-ksr-tag-below-precision-rounds-to-zero.phpt b/tests/ext/priority_sampling/032-ksr-tag-below-precision-rounds-to-zero.phpt
@@ -0,0 +1,19 @@
+--TEST--
+_dd.p.ksr rounds rate below 6-decimal precision to 0
+--ENV--
+DD_TRACE_SAMPLING_RULES=[{"sample_rate": 0.0000001}]
+DD_TRACE_GENERATE_ROOT_SPAN=1
+--FILE--
+<?php
+$root = \DDTrace\root_span();
+
+\DDTrace\get_priority_sampling();
+
+$ksr = isset($root->meta["_dd.p.ksr"]) ? $root->meta["_dd.p.ksr"] : "-";
+echo "_dd.p.ksr = ", $ksr, "\n";
+// 0.0000001 rounds to 0 at 6 decimal places
+echo "no_sci_notation = ", (strpos($ksr, 'e') === false) ? "true" : "false", "\n";
+?>
+--EXPECT--
+_dd.p.ksr = 0
+no_sci_notation = true
