Initial commit with translated description

tests/tokens.test.js

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+const { describe, it } = require("node:test");
+const assert = require("node:assert");
+const { TOKEN_RATES, emptyUsageBucket, calculateCostForBucket } = require("../src/tokens");
+
+describe("tokens module", () => {
+  describe("TOKEN_RATES", () => {
+    it("has input rate", () => {
+      assert.strictEqual(TOKEN_RATES.input, 15.0);
+    });
+
+    it("has output rate", () => {
+      assert.strictEqual(TOKEN_RATES.output, 75.0);
+    });
+
+    it("has cache read rate", () => {
+      assert.strictEqual(TOKEN_RATES.cacheRead, 1.5);
+    });
+
+    it("has cache write rate", () => {
+      assert.strictEqual(TOKEN_RATES.cacheWrite, 18.75);
+    });
+  });
+
+  describe("emptyUsageBucket()", () => {
+    it("returns object with zero values", () => {
+      const bucket = emptyUsageBucket();
+      assert.strictEqual(bucket.input, 0);
+      assert.strictEqual(bucket.output, 0);
+      assert.strictEqual(bucket.cacheRead, 0);
+      assert.strictEqual(bucket.cacheWrite, 0);
+      assert.strictEqual(bucket.cost, 0);
+      assert.strictEqual(bucket.requests, 0);
+    });
+
+    it("returns a new object each time", () => {
+      const a = emptyUsageBucket();
+      const b = emptyUsageBucket();
+      assert.notStrictEqual(a, b);
+      a.input = 100;
+      assert.strictEqual(b.input, 0);
+    });
+  });
+
+  describe("calculateCostForBucket()", () => {
+    it("calculates cost for given token counts", () => {
+      const bucket = {
+        input: 1_000_000,
+        output: 1_000_000,
+        cacheRead: 1_000_000,
+        cacheWrite: 1_000_000,
+      };
+      const result = calculateCostForBucket(bucket);
+      assert.strictEqual(result.inputCost, 15.0);
+      assert.strictEqual(result.outputCost, 75.0);
+      assert.strictEqual(result.cacheReadCost, 1.5);
+      assert.strictEqual(result.cacheWriteCost, 18.75);
+      assert.strictEqual(result.totalCost, 15.0 + 75.0 + 1.5 + 18.75);
+    });
+
+    it("returns zero cost for empty bucket", () => {
+      const bucket = { input: 0, output: 0, cacheRead: 0, cacheWrite: 0 };
+      const result = calculateCostForBucket(bucket);
+      assert.strictEqual(result.totalCost, 0);
+    });
+
+    it("accepts custom rates", () => {
+      const bucket = { input: 1_000_000, output: 0, cacheRead: 0, cacheWrite: 0 };
+      const customRates = { input: 10, output: 0, cacheRead: 0, cacheWrite: 0 };
+      const result = calculateCostForBucket(bucket, customRates);
+      assert.strictEqual(result.inputCost, 10.0);
+      assert.strictEqual(result.totalCost, 10.0);
+    });
+
+    it("calculates proportionally for partial token counts", () => {
+      const bucket = { input: 500_000, output: 0, cacheRead: 0, cacheWrite: 0 };
+      const result = calculateCostForBucket(bucket);
+      assert.strictEqual(result.inputCost, 7.5);
+    });
+  });
+});