First commit, phased 1 and 2 created but untested

tests/unit/energy.test.js

@@ -0,0 +1,90 @@
+const test = require('node:test');
+const assert = require('node:assert/strict');
+const { computeEnergy, ENERGY_MAX, ENERGY_REGEN_SECONDS } = require('../../src/game/energy');
+
+// No time passed
+test('computeEnergy no time passed', () => {
+  const now = Date.now();
+  const result = computeEnergy(50, now, now);
+  assert.equal(result.energy, 50);
+  assert.equal(result.updatedAtMs, now);
+});
+
+// Clock going backwards
+test('computeEnergy clock going backwards', () => {
+  const result = computeEnergy(50, Date.now(), Date.now() - 100000);
+  assert.equal(result.energy, 50);
+});
+
+// Less than one regen interval
+test('computeEnergy partial tick (less than 1 regen interval)', () => {
+  const now = Date.now();
+  const result = computeEnergy(50, now - 10000, now);
+  // 10s < 180s → no regen
+  assert.equal(result.energy, 50);
+});
+
+// One full tick
+test('computeEnergy one full tick', () => {
+  const now = Date.now();
+  const result = computeEnergy(50, now - 180000, now);
+  // 180s / 180s = 1 tick
+  assert.equal(result.energy, 51);
+});
+
+// Multiple full ticks
+test('computeEnergy multiple full ticks', () => {
+  const now = Date.now();
+  const result = computeEnergy(50, now - 360000, now);
+  // 360s / 180s = 2 ticks
+  assert.equal(result.energy, 52);
+});
+
+// Caps at max
+test('computeEnergy caps at max', () => {
+  const now = Date.now();
+  const result = computeEnergy(100, now - 3600000, now);
+  assert.equal(result.energy, ENERGY_MAX);
+});
+
+// Large gap (hours ago)
+test('computeEnergy large gap caps at max', () => {
+  const now = Date.now();
+  const result = computeEnergy(30, now - 36000000, now); // 10 hours ago
+  assert.equal(result.energy, ENERGY_MAX);
+});
+
+// Partial interval preserved (timestamp advances by whole ticks only)
+test('computeEnergy preserves partial interval', () => {
+  const updatedAt = 1000000;
+  const now = 1000000 + 180000 + 50000; // 1 tick + 50s partial
+  const result = computeEnergy(50, updatedAt, now);
+  assert.equal(result.energy, 51);
+  // Timestamp should advance by exactly 1 tick, not the full elapsed
+  assert.equal(result.updatedAtMs, updatedAt + 180000);
+});
+
+// Starting from zero
+test('computeEnergy from zero', () => {
+  const now = Date.now();
+  const result = computeEnergy(0, now - 540000, now);
+  // 540s / 180s = 3 ticks → 0 + 3 = 3
+  assert.equal(result.energy, 3);
+});
+
+// At max, large gap → resets timestamp
+test('computeEnergy at max resets timestamp', () => {
+  const now = Date.now();
+  const result = computeEnergy(100, now - 10000000, now);
+  assert.equal(result.energy, ENERGY_MAX);
+  assert.equal(result.updatedAtMs, now);
+});
+
+// Constants are correct
+test('ENERGY_MAX is 100', () => {
+  assert.equal(ENERGY_MAX, 100);
+});
+
+test('ENERGY_REGEN_SECONDS is 180', () => {
+  assert.equal(ENERGY_REGEN_SECONDS, 180);
+});