LibJS: Test function toBeCloseTo takes an optional precision argument

Modeled after the equivalent Jest function.
https://jestjs.io/docs/expect#tobeclosetonumber-numdigits

Userland/Libraries/LibJS/Tests/test-common-tests.js

@@ -36,6 +36,16 @@ test("toBeCloseTo", () => {
     expect(1).not.toBeCloseTo(1.00001);
     expect(1).toBeCloseTo(1.000001);
 
+    expect(1).not.toBeCloseTo(1.001, 3);
+    expect(1).toBeCloseTo(1.001, 2);
+    expect(1).not.toBeCloseTo(0, 0);
+    expect(6).toBeCloseTo(10, -1);
+    expect(125).toBeCloseTo(100, -2);
+    expect(3.14159).toBeCloseTo(3.14158, 4);
+    expect(() => {
+        expect(1).toBeCloseTo(1, "foo").toThrow(ExpectationError);
+    }).toThrow(ExpectationError);
+
     [
         ["foo", 1],
         [1, "foo"],

Userland/Libraries/LibJS/Tests/test-common.js

@@ -86,8 +86,7 @@ class ExpectationError extends Error {
             });
         }
 
-        // FIXME: Take a precision argument like jest's toBeCloseTo matcher
-        toBeCloseTo(value) {
+        toBeCloseTo(value, precision = 5) {
             this.__expect(
                 typeof this.target === "number",
                 () => `toBeCloseTo: expected target of type number, got ${typeof this.target}`
@@ -96,9 +95,14 @@ class ExpectationError extends Error {
                 typeof value === "number",
                 () => `toBeCloseTo: expected argument of type number, got ${typeof value}`
             );
+            this.__expect(
+                typeof precision === "number",
+                () => `toBeCloseTo: expected precision of type number, got ${typeof precision}`
+            );
 
+            const epsilon = 10 ** -precision / 2;
             this.__doMatcher(() => {
-                this.__expect(Math.abs(this.target - value) < 0.000001);
+                this.__expect(Math.abs(this.target - value) < epsilon);
             });
         }