test(bootstrapper): add comprehensive tests for iterative bootstrap

Add 47 unit tests in test_bootstrapper_iterative.py covering all new
iterative bootstrap components: BootstrapPhase, WorkItem, _track_why,
_create_unresolved_work_items, _phase_resolve, _phase_start,
_phase_complete, _dispatch_phase, _handle_phase_error (all error
modes), and end-to-end loop tests for phase lifecycle, LIFO ordering,
multiple versions error isolation, and test mode continuation.

Add e2e/test_bootstrap_iterative.sh that bootstraps stevedore==5.2.0
and verifies build-order dependency ordering and graph structure.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
Signed-off-by: Rohan Devasthale <rdevasth@redhat.com>

Author: rd4398

e2e/test_bootstrap_iterative.sh

@@ -0,0 +1,76 @@
+#!/bin/bash
+# -*- indent-tabs-mode: nil; tab-width: 2; sh-indentation: 2; -*-
+
+# Tests that the iterative bootstrap produces correct results for a
+# package with transitive dependencies. Verifies that the LIFO-based
+# iterative loop builds dependencies in the correct order (deps before
+# their dependents) and that the build-order.json and graph.json are
+# consistent.
+
+SCRIPTDIR="$( cd "$( dirname "${BASH_SOURCE[0]}" )" && pwd )"
+source "$SCRIPTDIR/common.sh"
+
+fromager \
+  --log-file="$OUTDIR/bootstrap.log" \
+  --error-log-file="$OUTDIR/fromager-errors.log" \
+  --sdists-repo="$OUTDIR/sdists-repo" \
+  --wheels-repo="$OUTDIR/wheels-repo" \
+  --work-dir="$OUTDIR/work-dir" \
+  bootstrap 'stevedore==5.2.0'
+
+# Verify expected output files exist
+EXPECTED_FILES="
+$OUTDIR/wheels-repo/downloads/setuptools-*.whl
+$OUTDIR/wheels-repo/downloads/pbr-*.whl
+$OUTDIR/wheels-repo/downloads/stevedore-*.whl
+$OUTDIR/work-dir/build-order.json
+$OUTDIR/work-dir/graph.json
+"
+
+pass=true
+for pattern in $EXPECTED_FILES; do
+  if [ ! -f "${pattern}" ]; then
+    echo "Did not find $pattern" 1>&2
+    pass=false
+  fi
+done
+
+# Verify build order: dependencies must appear before dependents
+# pbr and setuptools must come before stevedore in build-order.json
+BUILD_ORDER="$OUTDIR/work-dir/build-order.json"
+pbr_idx=$(python3 -c "
+import json, sys
+data = json.load(open('$BUILD_ORDER'))
+dists = [e['dist'] for e in data]
+print(dists.index('pbr') if 'pbr' in dists else -1)
+")
+stevedore_idx=$(python3 -c "
+import json, sys
+data = json.load(open('$BUILD_ORDER'))
+dists = [e['dist'] for e in data]
+print(dists.index('stevedore') if 'stevedore' in dists else -1)
+")
+
+if [ "$pbr_idx" -ge "$stevedore_idx" ] || [ "$pbr_idx" -eq "-1" ]; then
+  echo "ERROR: pbr (idx=$pbr_idx) must appear before stevedore (idx=$stevedore_idx) in build order" 1>&2
+  pass=false
+fi
+
+# Verify graph.json has the expected dependency edges
+python3 -c "
+import json, sys
+graph = json.load(open('$OUTDIR/work-dir/graph.json'))
+# stevedore should exist as a node
+stevedore_nodes = [k for k in graph if k.startswith('stevedore==')]
+if not stevedore_nodes:
+    print('ERROR: stevedore not found in graph', file=sys.stderr)
+    sys.exit(1)
+# pbr should exist as a node
+pbr_nodes = [k for k in graph if k.startswith('pbr==')]
+if not pbr_nodes:
+    print('ERROR: pbr not found in graph', file=sys.stderr)
+    sys.exit(1)
+print('Graph structure verified')
+" || pass=false
+
+$pass