Compare code and failure modes

Problem

What becomes confusing, fragile, or impossible without understanding compare code and failure modes? This lesson answers that through explanation, a worked example, two runnable exercises, and a reference solution. No teacher-supplied worksheet is required.

HTTP and hypertext scale by exchanging representations through standardized methods, status codes, headers, links, and forms.

Concept explanation

Compare code and failure modes belongs to “Earn HTMX by comparison”. compare code and failure modes is retrieval day: rebuild core behavior without notes, then compare evidence and teach corrections.

For compare code and failure modes, trace concrete input, state transition, output, and failure through a request/response contract whose method, status, headers, representation, and next actions are observable.

A client sends a request; a server returns a representation plus metadata. Hypermedia controls advertise valid next actions. Apply that model to supplied normal, boundary, and failure cases; each case below names its input and expected evidence.

Example bank

Compare normal, boundary, failure, and cross-layer cases. Predict each observation before revealing the explanation.

Worked example

Start from supplied lab.sh. Focus: Close notes and recreate compare code and failure modes from blank starting state using: Implement same form workflow as full-page HTML, fetch, and HTMX variants.

1. Run: chmod +x lab.sh && ./lab.sh
2. Save baseline evidence. Compare curl -v output, request method, status, cache metadata, redirects, and representation bytes.
3. Boundary case: Without rereading, predict and handle: Disable script and compare baseline recovery.
4. Failure case: Diagnose from memory, then consult reference only after capturing evidence: Return 500 during partial update and inspect user-visible state.

RESULT
Rebuilt version reproduces Comparison counts code, requests, failure paths, focus behavior, and server contract for each variant.; correction log names every memory gap. Starter-level baseline: headers.txt begins with an HTTP status line; body.txt contains the representation; byte count is greater than zero.

Starter material

Create lab.sh, paste this exact content, then run the command below.

#!/usr/bin/env sh
set -eu
url="${1:-https://example.com/}"
printf '%s\n' '# compare code and failure modes'
curl -sS -D headers.txt -o body.txt "$url"
sed -n '1,12p' headers.txt
printf 'body bytes: ' && wc -c < body.txt

STOP / CLEANUPNo background process. Remove headers.txt and body.txt only after saving evidence.

Independent exercise

Teach at three depths: compare code and failure modes

1. Create second case from blank file: Without rereading, predict and handle: Disable script and compare baseline recovery.
2. Then create controlled failure: Diagnose from memory, then consult reference only after capturing evidence: Return 500 during partial update and inspect user-visible state.
3. Use curl · Chromium Network · server logs to prove behavior, then repair controlled failure.
4. Compare result against supplied acceptance checks and reference approach before marking complete.

Expected result

• Rebuilt version reproduces Comparison counts code, requests, failure paths, focus behavior, and server contract for each variant.; correction log names every memory gap.
• headers.txt begins with an HTTP status line; body.txt contains the representation; byte count is greater than zero.
• Controlled compare code and failure modes failure produces captured evidence; repair restores stated invariant without hiding error.

Hints

Solution

Attempt both exercises before opening reference approach.