Session 28: Parlay builder, line movement tracker, book comparison — 3 features, zero credits (1623 tests)

2026-06-13 12:37:08 -04:00
parent 66fafd8429
commit c48aecd510
23 changed files with 1567 additions and 1 deletions
@@ -0,0 +1,68 @@
+// Unit: book comparison service (Session 28). Pure functions.
+
+const { compareProp, bestLines } = require('../../src/services/bookComparisonService');
+
+const prop = {
+  player: 'Wembanyama',
+  stat_type: 'points',
+  lines: [
+    { book: 'draftkings', line: 28.5, over_odds: -110, under_odds: -110 },
+    { book: 'fanduel', line: 28.5, over_odds: -105, under_odds: -115 }, // best over
+    { book: 'betmgm', line: 28.5, over_odds: -120, under_odds: -102 },  // best under
+  ],
+};
+
+describe('bookComparisonService — compareProp', () => {
+  test('identifies the best OVER line (highest payout)', () => {
+    const c = compareProp(prop, 'over');
+    expect(c.bestBook).toBe('fanduel'); // -105 pays more than -110/-120
+    expect(c.bestOdds).toBe(-105);
+    expect(c.books.find((b) => b.book === 'fanduel').isBest).toBe(true);
+    expect(c.bookCount).toBe(3);
+  });
+
+  test('identifies the best UNDER line', () => {
+    const c = compareProp(prop, 'under');
+    expect(c.bestBook).toBe('betmgm'); // -102 pays more than -110/-115
+    expect(c.bestOdds).toBe(-102);
+  });
+
+  test('savings is positive (best beats the field average)', () => {
+    const c = compareProp(prop, 'over');
+    expect(c.savings).toBeGreaterThan(0);
+  });
+
+  test('single-book prop still compares (bookCount 1)', () => {
+    const c = compareProp({ player: 'X', stat_type: 'hits', lines: [{ book: 'dk', over_odds: -110 }] }, 'over');
+    expect(c.bookCount).toBe(1);
+    expect(c.bestBook).toBe('dk');
+  });
+
+  test('no usable lines → null, not crash', () => {
+    expect(compareProp({ player: 'X', stat_type: 'hits', lines: [] }, 'over')).toBeNull();
+    expect(compareProp({ player: 'X', stat_type: 'hits' }, 'over')).toBeNull();
+  });
+});
+
+describe('bookComparisonService — bestLines', () => {
+  test('drops single-book props and sorts by savings desc', () => {
+    const props = [
+      prop,
+      { player: 'Solo', stat_type: 'reb', lines: [{ book: 'dk', over_odds: -110 }] }, // 1 book → dropped
+      {
+        player: 'BigEdge', stat_type: 'ast',
+        lines: [
+          { book: 'dk', over_odds: -200 },
+          { book: 'fd', over_odds: +120 }, // huge spread → big savings
+        ],
+      },
+    ];
+    const lines = bestLines(props, { side: 'over' });
+    expect(lines.map((l) => l.player)).not.toContain('Solo');
+    expect(lines[0].player).toBe('BigEdge'); // biggest savings first
+  });
+
+  test('non-array input → empty', () => {
+    expect(bestLines(null)).toEqual([]);
+  });
+});