fix

src/collection/min-heap.ts

@@ -32,6 +32,7 @@ export class MinHeap<T> {
     this.tree[i] = value;
 
     while (i && isBefore(this.order, value /* i.e. this.tree[i] */, this.tree[j])) {
+      // pop up new value
       this.tree[i] = this.tree[j];
       this.tree[j] = value;
 
@@ -134,7 +135,7 @@ export class MinHeap<T> {
   private assertInvariants() {
     for (let i = 1; i < this.tree.length; i++) {
       const p = positions.parent(i);
-      if (!this.order.compare(this.tree[p], this.tree[i])) {
+      if (!isBefore(this.order, this.tree[p], this.tree[i])) {
         throw new Error(`MinHeap#assertInvariants(): expected this.tree[${p} to be ordered before this.tree[${i}]`);
       }
     }

src/collection/multiset.spec.ts

@@ -2,7 +2,7 @@ import { Multiset } from './multiset';
 
 describe(Multiset, () => {
   it('keeps elements and count', () => {
-    const testee = new Multiset<string>(false);
+    const testee = new Multiset<string>();
 
     testee.setCount('abc', 1);
     testee.setCount('abc', 2);
@@ -17,7 +17,7 @@ describe(Multiset, () => {
     testee.setCount('abc', 1);
     testee.setCount('abc', 1);
     testee.setCount('abc', 0);
-    expect(testee.maxCount()).toEqual(1);
+    expect(testee.maxCount()).toBe(1);
     expect(testee.getCount('abc')).toEqual(0);
     expect(testee.getCount('abd')).toEqual(1);
     expect(testee.findByCount(0)).toEqual(['abc']);

src/collection/multiset.ts

@@ -4,8 +4,6 @@ export class Multiset<T> {
   private map = new DefaultMap</* count */ number, /* objects */ Set<T>>((k) => new Set());
   private countMap = new Map</* object*/ T, /* count */ number>();
 
-  constructor(readonly removeOnZeroFreq = true) {}
-
   setCount(obj: T, count: number): void {
     const existedCount = this.countMap.get(obj);
 
@@ -18,7 +16,7 @@ export class Multiset<T> {
 
       const existedSet = this.map.get(existedCount)!;
       existedSet.delete(obj);
-      if (!existedSet.size && this.removeOnZeroFreq) {
+      if (!existedSet.size) {
         this.map.delete(existedCount);
       }
     } else {