Produce the connectivity decision tree and test it against four real faults

applied · 45 min · Objective 3.2

Task

Build a decision tree that takes "the internet is not working on my phone" to a cause in the fewest tests, then run it against four faults you create and can reverse. The tree is the deliverable, and testing it is what turns it from a diagram into something usable.

Steps

  1. Write lab/mobtree/tree.md as a numbered decision tree, each node a test with its two branches, reaching a cause in no more than four tests.
  2. Create four reversible faults and record them in lab/mobtree/faults.csv with header fault,how_created,how_reversed.
  3. Run the tree against each fault without looking at what you created, and record the path in lab/mobtree/runs.csv with header fault,tests_used,cause_found,correct.
  4. Reverse every fault and confirm the device is as it started, recording the confirmation in lab/mobtree/restored.txt.
  5. Write lab/mobtree/revision.md describing what you changed in the tree after testing it, and why.

Verify

grep -Ec '^[0-9]+\.' lab/mobtree/tree.md
awk -F, 'NR>1 && NF>=3 {n++} END {print n" fault(s) created and reversed"}' lab/mobtree/faults.csv
awk -F, 'NR>1 && NF>=4 {n++} END {print n" run(s)"}' lab/mobtree/runs.csv
awk -F, 'NR>1 && $2+0 > 4 {n++} END {print n" run(s) that took more than four tests"}' lab/mobtree/runs.csv
grep -c . lab/mobtree/restored.txt
grep -Ec '^[-*0-9]' lab/mobtree/revision.md

Four numbered tree steps, four faults created and reversed, four runs, and a revision note. A tree that needed no revision after four real tests was either very good or was not followed.

Notes

The browser test belongs near the top of any tree you build. If a web page loads, the network is fine and the problem is the application -- and that is one test that eliminates an entire layer.

This is an independent study companion for CompTIA A+ Core 2 220-1202 and is not produced by or endorsed by CompTIA.