Add comprehensive ERT test suite and fix critical bugs

Session 1: Testing infrastructure and initial test coverage

Bug fixes in wttrin.el:
- Fix wttrin-additional-url-params to handle nil unit system
- Remove incorrect callback parameter to url-retrieve-synchronously
- Add nil buffer check for network failures
- Strip HTTP headers before decoding response
- Kill buffer after fetch to prevent memory leaks
- Fix double concatenation of URL params in cache function
- Add proper URL encoding via new wttrin--build-url function

Refactoring:
- Extract wttrin--build-url as pure, testable function
- Separate URL building logic from network I/O

Test infrastructure (33 tests, 100% passing):
- tests/testutil-wttrin.el: Shared test utilities
- tests/test-wttrin-additional-url-params.el: 7 tests
- tests/test-wttrin--make-cache-key.el: 9 tests
- tests/test-wttrin--build-url.el: 10 tests
- tests/test-wttrin--cleanup-cache-if-needed.el: 7 tests

Documentation:
- docs/testing-plan.org: Comprehensive testing roadmap
- docs/bugs.org: Bug analysis from code review
- docs/NOTES.org: Session tracking and guidelines
- docs/session-1-summary.org: Detailed session summary

Next session: Cache workflow tests, parsing logic extraction, integration tests

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>

1 files changed, 91 insertions, 0 deletions

diff --git a/tests/test-wttrin--build-url.el b/tests/test-wttrin--build-url.el
new file mode 100644
index 0000000..21d3241
--- /dev/null
+++ b/tests/test-wttrin--build-url.el
@@ -0,0 +1,91 @@
+;;; test-wttrin--build-url.el --- Tests for wttrin--build-url -*- lexical-binding: t; -*-
+
+;; Copyright (C) 2025 Craig Jennings
+
+;;; Commentary:
+
+;; Unit tests for wttrin--build-url function.
+;; Tests URL construction with proper encoding and parameters.
+
+;;; Code:
+
+(require 'ert)
+(require 'wttrin)
+(require 'testutil-wttrin)
+
+;;; Normal Cases
+
+(ert-deftest test-wttrin--build-url-normal-simple-location-returns-url ()
+  "Test that simple location builds correct URL."
+  (testutil-wttrin-with-unit-system nil
+    (should (equal "https://wttr.in/Paris?A"
+                   (wttrin--build-url "Paris")))))
+
+(ert-deftest test-wttrin--build-url-normal-location-with-metric-returns-url ()
+  "Test that location with metric unit system builds correct URL."
+  (testutil-wttrin-with-unit-system "m"
+    (should (equal "https://wttr.in/London?mA"
+                   (wttrin--build-url "London")))))
+
+(ert-deftest test-wttrin--build-url-normal-location-with-uscs-returns-url ()
+  "Test that location with USCS unit system builds correct URL."
+  (testutil-wttrin-with-unit-system "u"
+    (should (equal "https://wttr.in/Berlin?uA"
+                   (wttrin--build-url "Berlin")))))
+
+;;; Boundary Cases
+
+(ert-deftest test-wttrin--build-url-boundary-location-with-spaces-encodes-url ()
+  "Test that location with spaces is properly URL-encoded."
+  (testutil-wttrin-with-unit-system nil
+    (should (equal "https://wttr.in/New%20York?A"
+                   (wttrin--build-url "New York")))))
+
+(ert-deftest test-wttrin--build-url-boundary-location-with-comma-encodes-url ()
+  "Test that location with comma is properly URL-encoded."
+  (testutil-wttrin-with-unit-system nil
+    (should (equal "https://wttr.in/New%20York%2C%20NY?A"
+                   (wttrin--build-url "New York, NY")))))
+
+(ert-deftest test-wttrin--build-url-boundary-location-with-special-chars-encodes-url ()
+  "Test that location with special characters is properly URL-encoded."
+  (testutil-wttrin-with-unit-system "m"
+    ;; ~Eiffel+Tower format is used by wttr.in for landmarks
+    ;; ~ is an unreserved character (RFC 3986) and is not encoded
+    ;; + is encoded as %2B
+    (should (equal "https://wttr.in/~Eiffel%2BTower?mA"
+                   (wttrin--build-url "~Eiffel+Tower")))))
+
+(ert-deftest test-wttrin--build-url-boundary-unicode-location-encodes-url ()
+  "Test that Unicode location is properly URL-encoded."
+  (testutil-wttrin-with-unit-system nil
+    ;; Unicode should be properly encoded
+    (let ((result (wttrin--build-url "東京")))
+      (should (string-prefix-p "https://wttr.in/" result))
+      (should (string-suffix-p "?A" result))
+      ;; Should contain URL-encoded Unicode
+      (should (string-match-p "%[0-9A-F][0-9A-F]" result)))))
+
+(ert-deftest test-wttrin--build-url-boundary-empty-location-returns-url ()
+  "Test that empty location builds URL with empty query."
+  (testutil-wttrin-with-unit-system nil
+    (should (equal "https://wttr.in/?A"
+                   (wttrin--build-url "")))))
+
+(ert-deftest test-wttrin--build-url-boundary-gps-coordinates-encodes-url ()
+  "Test that GPS coordinates are properly URL-encoded."
+  (testutil-wttrin-with-unit-system nil
+    ;; Format: -78.46,106.79
+    (should (equal "https://wttr.in/-78.46%2C106.79?A"
+                   (wttrin--build-url "-78.46,106.79")))))
+
+;;; Error Cases
+
+(ert-deftest test-wttrin--build-url-error-nil-location-signals-error ()
+  "Test that nil location signals an error."
+  (testutil-wttrin-with-unit-system nil
+    (should-error (wttrin--build-url nil)
+                  :type 'error)))
+
+(provide 'test-wttrin--build-url)
+;;; test-wttrin--build-url.el ends here