Add fix-bug, add-test, and review-pr agent skills

.agents/skills/add-test/SKILL.md

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+---
+name: add-test
+description: >
+  Add integration or unit tests to an OpenROAD module. Handles the
+  complete workflow: writing the Tcl/C++ test, generating golden files,
+  and registering the test in BOTH CMake and Bazel build systems (the
+  most common mistake is forgetting Bazel registration). Use when asked
+  to add tests, improve test coverage, create regression tests, or write
+  unit tests for any OpenROAD module (ant, cts, dpl, drt, gpl, grt, mpl,
+  odb, pad, pdn, psm, rcx, rsz, sta, stt, tap, upf, utl, etc.).
+  Also triggers on: "add test", "write test", "test coverage",
+  "missing tests", "create regression test", "add unit test".
+argument-hint: "<module> [test-description]"
+---
+
+# Add Test to OpenROAD Module
+
+You are adding tests for: **$ARGUMENTS**
+
+## 1. Identify the module and scope
+
+Parse `$ARGUMENTS` to determine:
+- **Module name** (e.g., `rsz`, `drt`, `gpl`)
+- **What to test** (specific feature, edge case, or general coverage)
+
+Explore existing tests to understand conventions:
+```bash
+ls src/MODULE/test/*.tcl | head -20
+```
+
+Read a representative test for the module's style:
+```bash
+# Good reference for integration test patterns:
+cat src/rsz/test/repair_tie12_hier.tcl
+```
+
+## 2. Write the integration test (Tcl)
+
+Create `src/MODULE/test/TEST_NAME.tcl`:
+
+```tcl
+# Brief description of what this test verifies
+set test_name TEST_NAME
+source "helpers.tcl"
+
+# Read design files
+read_lef "TECH.lef"
+read_lef "CELLS.lef"
+read_def "DESIGN.def"
+
+# ... test operations ...
+
+# Use make_result_file for temporary output
+set def_filename "${test_name}.def"
+set out_def [make_result_file $def_filename]
+write_def $out_def
+
+# Compare against golden file
+diff_file ${test_name}.defok $out_def
+```
+
+### Test design files
+
+Prefer reusing existing test data in `src/MODULE/test/`. Only create
+new LEF/DEF files when testing a specific geometry or edge case that
+existing files don't cover. Keep test data minimal.
+
+### Naming conventions
+
+- Test files: `src/MODULE/test/TEST_NAME.tcl`
+- Golden log: `src/MODULE/test/TEST_NAME.ok`
+- Golden output: `src/MODULE/test/TEST_NAME.{defok,vok,spefok,...}`
+- Test data: `src/MODULE/test/*.{lef,def,lib,sdc,v}`
+
+## 3. Generate golden files
+
+Run the test and capture output:
+```bash
+cd src/MODULE/test
+
+# Run with openroad to generate output
+openroad -no_splash -no_init -exit TEST_NAME.tcl > TEST_NAME.ok 2>&1
+
+# Remove the openroad banner from the .ok file if present
+# The .ok file should contain only the test's stdout
+```
+
+If the test uses `diff_file`, also generate the golden output file
+(e.g., `TEST_NAME.defok`) by running once and copying the result file.
+
+## 4. Register in BOTH build systems
+
+This is the most common mistake. **Every test must be in both CMake AND
+Bazel.** CMake-only tests silently pass locally but are missing from
+Bazel CI.
+
+### CMake -- `src/MODULE/test/CMakeLists.txt`
+
+Find the `or_integration_tests()` call. The first positional argument
+is the **module name**, followed by the `TESTS` keyword and the list:
+
+```cmake
+or_integration_tests(
+  "MODULE"           # <-- module name (e.g. "rsz")
+  TESTS
+    existing_test1
+    existing_test2
+    TEST_NAME        # <-- add here
+)
+```
+
+Some modules also have a `PASSFAIL_TESTS` section after `TESTS` -- add
+to the appropriate list. Look at the module's existing `CMakeLists.txt`
+before editing.
+
+### Bazel -- `src/MODULE/test/BUILD`
+
+The typical pattern is a `TESTS` list consumed by a list comprehension
+that calls `regression_test()` for each name:
+
+```python
+TESTS = [
+    "buffer_ports1",
+    "buffer_ports10",
+    "buffer_ports11",
+    "TEST_NAME",     # <-- add here, in the existing sort order
+    # (other tests omitted)
+]
+
+[
+    regression_test(
+        name = test_name,
+    )
+    for test_name in TESTS
+]
+```
+
+Some modules split tests across multiple lists (`TESTS`,
+`PASSFAIL_TESTS`, `BIG_TESTS`, etc.) and define a combined
+`ALL_TESTS = TESTS + PASSFAIL_TESTS + ...` that the comprehension
+iterates over. Read the existing `BUILD` to find which list to
+extend, and insert the new test name in whatever sort order that
+file already uses (most modules are alphabetical).
+
+## 5. Write unit tests (C++, if applicable)
+
+Prefer C++ unit tests over Tcl for testing internal logic, algorithms,
+and data structure operations. Use Tcl integration tests for
+command-level behavior and end-to-end flows.
+
+### Test file
+
+Create `src/MODULE/test/cpp/TestName.cpp`:
+
+```cpp
+#include "gtest/gtest.h"
+#include "odb/db.h"
+
+// Simple test (no fixture)
+namespace module {
+namespace {
+
+TEST(ModuleTest, TestDescription) {
+  // ARRANGE - ACT - ASSERT
+  EXPECT_EQ(expected, actual);
+}
+
+}  // namespace
+}  // namespace module
+```
+
+### Using test fixtures
+
+OpenROAD provides a fixture hierarchy for tests that need database
+or tool setup. Choose the simplest one that covers your needs:
+
+| Fixture | Use when |
+|---------|----------|
+| `tst::Fixture` | Need bare `dbDatabase` + STA, load LEFs manually |
+| `tst::Nangate45Fixture` | Need pre-loaded Nangate45 tech/lib |
+| `tst::Sky130Fixture` | Need pre-loaded Sky130 tech/lib |
+| `tst::IntegratedFixture` | Need full tool integration (STA, DPL, GRT, RSZ) |
+
+```cpp
+#include "gtest/gtest.h"
+#include "tst/nangate45_fixture.h"
+
+class TestFeature : public tst::Nangate45Fixture
+{
+ protected:
+  void SetUp() override { /* additional setup */ }
+};
+
+TEST_F(TestFeature, HandlesEdgeCase) {
+  // block_, lib_ are available from the fixture
+  EXPECT_TRUE(condition);
+}
+```
+
+### CMake registration -- `src/MODULE/test/cpp/CMakeLists.txt`
+
+```cmake
+add_executable(TestName TestName.cpp)
+target_link_libraries(TestName
+    MODULE_lib
+    GTest::gtest
+    GTest::gtest_main
+    tst
+    odb
+)
+gtest_discover_tests(TestName
+    WORKING_DIRECTORY ${CMAKE_CURRENT_SOURCE_DIR}/..
+)
+add_dependencies(build_and_test TestName)
+```
+
+### Bazel registration -- `src/MODULE/test/BUILD`
+
+Add the `cc_test` target alongside the existing `regression_test`
+entries. Most modules keep C++ tests in the same BUILD file:
+
+```python
+load("@rules_cc//cc:cc_test.bzl", "cc_test")
+
+cc_test(
+    name = "TestName",
+    srcs = ["cpp/TestName.cpp"],
+    deps = [
+        "//src/MODULE",
+        "//src/tst",
+        "//src/tst:nangate45_fixture",  # if using Nangate45Fixture
+        "@googletest//:gtest",
+        "@googletest//:gtest_main",
+    ],
+)
+```
+
+## 6. Run and verify
+
+`./regression` is a thin ctest wrapper that filters by module label, so
+the standard ctest flags apply. Use `-R` to match a single test by name:
+
+```bash
+cd src/MODULE/test
+./regression -R TEST_NAME
+
+# Verify test is discoverable in both systems
+cd ../../../build
+ctest -N | grep MODULE.*TEST_NAME
+```
+
+## 7. Format and commit
+
+```bash
+# Format any C++ files (NEVER format src/sta/* or *.i files)
+clang-format -i <changed-cpp-files>
+
+git add src/MODULE/test/TEST_NAME.tcl \
+        src/MODULE/test/TEST_NAME.ok \
+        src/MODULE/test/CMakeLists.txt \
+        src/MODULE/test/BUILD
+git commit -s -m "MODULE: add TEST_NAME test
+
+Test for DESCRIPTION."
+```
+
+## Checklist
+
+- [ ] Test runs successfully: `./regression -R TEST_NAME`
+- [ ] Golden file generated and committed
+- [ ] Registered in CMake `CMakeLists.txt`
+- [ ] Registered in Bazel `BUILD`
+- [ ] Test data is minimal (reuse existing files when possible)
+- [ ] C++ files formatted with clang-format
+- [ ] Commit is signed off (`-s`)

.agents/skills/fix-bug/SKILL.md

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+---
+name: fix-bug
+description: >
+  Fix an OpenROAD bug from a GitHub issue. Analyzes the issue, traces the
+  root cause through the codebase, implements the fix, creates regression
+  tests (registered in both CMake and Bazel), runs clang-format, and
+  prepares a signed-off commit. Use when given a bug report issue number,
+  error code (e.g. GPL-0305, DRT-0001, RSZ-2007), or when asked to fix a
+  bug in any OpenROAD module (ant, cts, dpl, drt, gpl, grt, mpl, odb,
+  pad, pdn, psm, rcx, rsz, sta, stt, tap, upf, utl, etc.).
+  Also triggers on: "fix issue", "debug this error", "resolve crash",
+  "fix segfault", "repair", "patch bug".
+argument-hint: <issue-number-or-error-code>
+---
+
+# Fix OpenROAD Bug
+
+You are fixing a bug related to **$ARGUMENTS**.
+
+## 1. Understand the bug
+
+If `$ARGUMENTS` is a GitHub issue number:
+```bash
+gh issue view $ARGUMENTS --repo The-OpenROAD-Project/OpenROAD \
+  --json title,body,labels,comments
+```
+
+Extract from the issue:
+- **Error string** (e.g. `GPL-0305`, `DRT-0001`) -- search for the exact message ID
+- **Module** -- infer from labels or error prefix
+- **Steps to reproduce** -- look for attached scripts, Tcl commands, or tarballs
+- **Stack trace** -- if a crash, identify the faulting function
+
+If `$ARGUMENTS` is an error code, search for it directly:
+```bash
+grep -rn "ERROR_CODE" src/MODULE/src/
+```
+
+## 2. Trace the root cause
+
+Follow OpenROAD's "trace bugs upstream" principle: find where the bad
+data is **created**, not where it is **reported**.
+
+1. Find the error message source:
+   ```bash
+   grep -rn "ERROR_ID" src/
+   ```
+2. Read the surrounding code to understand the condition that triggers it
+3. Trace the data flow backward -- who sets the offending value?
+4. Identify the actual bug location (often in a different function/file
+   from where the error is reported)
+
+**Critical constraint**: Never modify files under `src/sta/`. OpenSTA is
+managed upstream. If the root cause is in OpenSTA, report this finding
+instead of patching it.
+
+## 3. Implement the fix
+
+Follow the coding practices in `docs/agents/coding.md`. Pay special
+attention to `int64_t` for area calculations and removing unreachable
+code after `error()` or `throw`.
+
+## 4. Create regression test
+
+Every bug fix needs a test that reproduces the exact failure mode from
+the issue (same error code, same stack frame, same condition) so a
+future regression is caught immediately.
+
+Use the **add-test** skill (`.agents/skills/add-test/SKILL.md`) for the
+full workflow: writing the test, generating golden files, and
+registering in both CMake and Bazel.
+
+## 5. Format and commit
+
+```bash
+# Format changed C++ files (NEVER format src/sta/* or *.i files)
+clang-format -i <changed-cpp-files>
+
+# Stage and commit with DCO sign-off
+git add <changed-files>
+git commit -s -m "MODULE: fix BRIEF_DESCRIPTION
+
+Fixes #ISSUE_NUMBER"
+```
+
+## 6. Verify
+
+- [ ] Test passes: `cd src/MODULE/test && ./regression -R TEST_NAME`
+- [ ] No unintended changes: `git diff HEAD`
+- [ ] Test registered in both CMake and Bazel
+- [ ] No `src/sta/` files modified
+- [ ] C++ files formatted with clang-format
+- [ ] Commit is signed off (`-s`)