Applying tdd on select-only exercise

exercises/concept/intro-select/create_fixture.sql

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+DROP TABLE IF EXISTS weather_readings;
+CREATE TABLE weather_readings (
+  date        TEXT    NOT NULL,
+  location    TEXT    NOT NULL,
+  temperature INTEGER NOT NULL,
+  humidity    INTEGER NOT NULL
+);
+
+.mode csv
+.import ./data.csv weather_readings

exercises/concept/intro-select/data.csv

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+"2025-10-22","Portland",53,72
+"2025-10-22","Seattle",56,66
+"2025-10-22","Boise",60,55
+"2025-10-23","Portland",54,70
+"2025-10-23","Seattle",57,68
+"2025-10-23","Boise",62,58

exercises/concept/intro-select/intro-select.sql

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+CREATE TABLE all_data AS
+    -- Task 1. Select all records.
+    SELECT * FROM weather_readings
+;
+
+CREATE TABLE location_and_temperature AS
+    -- Task 2. Select only location and temperature data.
+    -- Expect failure
+    SELECT temperature FROM weather_readings
+;
+
+CREATE TABLE seattle AS
+    -- Task 3. Select all data for Seattle.
+    SELECT * FROM weather_readings WHERE location = 'Seattle'
+;
+
+CREATE TABLE limited_humidity AS
+    -- Task 4. Select all data where the humidity is between 60% and 70%.
+    -- Expect failure
+    SELECT * FROM weather_readings WHERE humidity BETWEEN 50 AND 62
+;
+.print "My debugging output:"
+SELECT humidity from weather_readings;
+
+CREATE TABLE location AS
+    -- Task 5. Select only location data.
+    SELECT location FROM weather_readings
+;
+
+CREATE TABLE unique_location AS
+    -- Task 5. Select only unique location data.
+    SELECT DISTINCT location FROM weather_readings
+;

exercises/concept/intro-select/intro-select_test.sql

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+-- Create database:
+.read ./create_fixture.sql
+
+-- ASK: How can we correlate user output with specific tests? One way is to add .output statements
+-- in the stub file. But that introduces more noise into the stub file.
+
+-- Run user solution and store results
+.mode markdown
+.output user_output.md
+.read ./intro-select.sql
+.shell rm -f ./results.db
+.save ./results.db
+
+.output
+
+-- Report results
+.shell bash ./report-results.sh results.db

exercises/concept/intro-select/report-results.sh

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+#!/usr/bin/env bash
+db_file=$1
+mapfile -t slugs < <(jq -r 'keys[]' test_data.json)
+
+# Generate result for each test
+for slug in "${slugs[@]}"; do
+    actual=$(sqlite3 -json $db_file "SELECT * FROM ${slug};")
+    if [[ -z "$actual" ]]; then
+        actual="[]"
+    fi
+    jq -n --slurpfile test_data test_data.json --argjson got "${actual}" --arg slug "${slug}" -f test-result.jq
+done > results.txt
+
+# Aggregate results
+jq -n --slurpfile results results.txt '$results' > output.json

exercises/concept/intro-select/test-result.jq

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+def columns:
+    if (. | length) == 0 then []
+    else .[0] | keys
+    end;
+
+def rows:
+    map(to_entries | map(.value));
+
+def failure_message(got; expected):
+    (got | columns | tostring)  as $got_columns
+    | (expected | columns | tostring) as $expected_columns
+    | if $got_columns != $expected_columns then
+        "Expected columns \($expected_columns); but got \($got_columns)"
+      else
+        (got | rows | tostring) as $got_rows
+        | (expected | rows | tostring) as $expected_rows
+        | "With columns \($got_columns)\nexpected \($expected_rows)\nbut got \($got_rows)"
+      end;
+
+$test_data[0][$slug]
+| del(.expected) as $entry 
+| if $got != .expected then 
+      $entry + {"status": "fail", "message": failure_message($got; .expected)} 
+  else 
+      $entry + {"status": "pass"} 
+  end

exercises/concept/intro-select/test_data.json

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+{
+    "all_data": {
+        "task_id": 1,
+        "description": "All data", 
+        "expected": [
+            {"date": "2025-10-22", "location": "Portland", "temperature": 53, "humidity": 72},
+            {"date": "2025-10-22", "location": "Seattle", "temperature": 56, "humidity": 66},
+            {"date": "2025-10-22", "location": "Boise", "temperature": 60, "humidity": 55},
+            {"date": "2025-10-23", "location": "Portland", "temperature": 54, "humidity": 70},
+            {"date": "2025-10-23", "location": "Seattle", "temperature": 57, "humidity": 68},
+            {"date": "2025-10-23", "location": "Boise", "temperature": 62, "humidity": 58}
+        ]
+    },
+    "location_and_temperature": {
+        "task_id": 2,
+        "description": "Just location and temperature",
+        "expected": [
+            {"location": "Portland", "temperature": 53},
+            {"location": "Seattle", "temperature": 56},
+            {"location": "Boise", "temperature": 60},
+            {"location": "Portland", "temperature": 54},
+            {"location": "Seattle", "temperature": 57},
+            {"location": "Boise", "temperature": 62}
+        ]
+    },
+    "seattle": {
+        "task_id": 3,
+        "description": "Seattle only",
+        "expected": [
+            {"date": "2025-10-22", "location": "Seattle", "temperature": 56, "humidity": 66},
+            {"date": "2025-10-23", "location": "Seattle", "temperature": 57, "humidity": 68}
+        ]
+    },
+    "limited_humidity": {
+        "task_id": 4,
+        "description": "Humidity within range",
+        "expected": [
+            {"date": "2025-10-22", "location": "Seattle", "temperature": 56, "humidity": 66},
+            {"date": "2025-10-23", "location": "Portland", "temperature": 54, "humidity": 70},
+            {"date": "2025-10-23", "location": "Seattle", "temperature": 57, "humidity": 68}
+        ]
+    },
+    "location": {
+        "task_id": 5,
+        "description": "Just locations",
+        "expected": [
+            {"location": "Portland"},
+            {"location": "Seattle"},
+            {"location": "Boise"},
+            {"location": "Portland"},
+            {"location": "Seattle"},
+            {"location": "Boise"}
+        ]
+    },
+    "unique_location": {
+        "task_id": 5,
+        "description": "Only unique locations",
+        "expected": [
+            {"location": "Portland"},
+            {"location": "Seattle"},
+            {"location": "Boise"}
+        ]
+    }
+}