test: writes some tests for the sampler prop

src/rian.test.ts

@@ -5,6 +5,7 @@ import * as assert from 'uvu/assert';
 
 import * as rian from 'rian';
 import * as utils from 'rian/utils';
+import { traceparent } from 'tctx';
 
 const noop = () => {};
 
@@ -229,9 +230,71 @@ buffer('flush all', async () => {
  assert.equal(spans[1].name, 'span 2');
 });
 
+const sampler = suite('sampler');
+
+sampler('should allow a sampler', async () => {
+ let should_sample = false;
+
+ const tracer = rian.tracer('test', {
+ sampler: () => should_sample,
+ });
+
+ tracer.span('not sampled')(() => { });
+ should_sample = true;
+ tracer.span('sampled')(() => { });
+
+ const exporter = spy<rian.Exporter>(returns);
+ const scopedSpans: rian.ScopedSpans[] = await rian.report(exporter);
+
+ assert.equal(scopedSpans.length, 1);
+ assert.equal(scopedSpans.at(0)!.spans.length, 1);
+ assert.equal(scopedSpans.at(0)?.spans.at(0)?.name, 'sampled');
+});
+
+sampler('allow a sampler to make a decision from its parent', async () => {
+ let no_parent_sample = true;
+
+ const S: rian.Sampler = (_id, parentId) => {
+ if (!parentId) return no_parent_sample;
+ return traceparent.is_sampled(parentId);
+ }
+
+ const tracer = rian.tracer('test', { sampler: S });
+
+ tracer.span('sampled#1')((s) => {
+ no_parent_sample = false;
+ s.span('sampled#1.1')(() => { })
+ });
+
+ no_parent_sample = false;
+ tracer.span('not sampled#1')((s) => {
+ s.span('not sampled#1.1')(() => { })
+ });
+
+ no_parent_sample = true;
+ tracer.span('sampled#2')((s) => {
+ s.span('sampled#2.1')(() => { })
+ });
+
+ no_parent_sample = false;
+
+ const exporter = spy<rian.Exporter>(returns);
+ const scopedSpans: rian.ScopedSpans[] = await rian.report(exporter);
+
+ assert.equal(scopedSpans.length, 1);
+ assert.equal(scopedSpans.at(0)!.spans.length, 4);
+ assert.equal(scopedSpans.at(0)!.spans.map(s => s.name), [
+ 'sampled#1',
+ 'sampled#1.1',
+ 'sampled#2',
+ 'sampled#2.1',
+ ]);
+});
+
 test.run();
 fn.run();
 measure.run();
 sampled.run();
 events.run();
 buffer.run();
+sampler.run();