chore: import upstream snapshot with attribution

docs/articles/testing.md

@@ -0,0 +1,80 @@
+## Run Tests From The Graph
+
+In Zerolang, `zero test` runs test blocks from graph inputs and graph-first packages. When
+this page shows `test` projection syntax, read it as the human review view of a
+graph-backed test declaration.
+
+```json-render
+{
+  "messages": [
+    {
+      "role": "user",
+      "text": "add subtract and prove it works"
+    },
+    {
+      "role": "assistant",
+      "text": "I’ll add the function and a focused test for it."
+    },
+    {
+      "role": "tools",
+      "calls": [
+        {
+          "command": "zero patch /tmp/subtract.patch",
+          "output": "program graph patch ok"
+        },
+        {
+          "command": "zero test --json --filter subtract",
+          "output": "{\"ok\":true,\"passedTests\":1,\"expectedFailures\":0}"
+        }
+      ]
+    }
+  ]
+}
+```
+
+## What This Means
+
+```zero
+test "add works" {
+    expect (add(40, 2) == 42)
+}
+```
+
+Agents should add or update tests through graph patches.
+
+## Daily Test Commands
+
+```sh
+zero test
+zero test --json
+zero test --json --filter add
+```
+
+Package tests discover test blocks across the package entry file and local
+modules. Filters use substring matching on the test name.
+
+## Expected Failures
+
+Expected-fail tests are named with `xfail:`, `expected fail:`, or `[xfail]`.
+
+| Result | JSON effect |
+| --- | --- |
+| The test fails as expected. | `expectedFailures` increments. |
+| The test passes unexpectedly. | `unexpectedPasses` increments and the command fails. |
+
+`zero test --json` includes `fixtures`, `snapshotKey`, selected/discovered
+counts, stdout/stderr, and per-test results.
+
+## Repository Reliability
+
+Repository-level reliability checks still live outside the docs site:
+
+```sh
+pnpm run reliability:smoke
+pnpm run native:sanitize
+pnpm run conformance
+```
+
+The reliability smoke covers golden output rows, structured snapshot rows,
+fuzz cases, and crasher regressions. Use those suites for compiler reliability,
+not per-page documentation assertions.