test(more tc for simple):

src/simple.ts

@@ -21,6 +21,7 @@ export class LazyCalc {
           : precision >= 0
           ? Math.min(precision, 292)
           : Math.max(precision, -292);
+
       if (precision) {
         // Shift with exponential notation to avoid floating-point issues.
         // See [MDN](https://mdn.io/round#Examples) for more details.

tests/unit/main.spec.ts

@@ -5,55 +5,10 @@ describe("base class", () => {
     const base = LazyBase.lazy(1);
     expect(base.value()).toBe(1);
   });
-  it("add", () => {
-    const base = LazyBase.lazy(1).add(4);
-    expect(base.value()).toBe(5);
-  });
-
-  it("subtract", () => {
-    const base = LazyBase.lazy(1).subtract(4);
-    expect(base.value()).toBe(-3);
-  });
-
-  it("multiply", () => {
-    const base = LazyBase.lazy(1).multiply(4);
-    expect(base.value()).toBe(4);
-  });
-  it("multiply - float", () => {
-    const base = LazyBase.lazy(1.5).multiply(4);
-    expect(base.value()).toBe(6);
-  });
-
-  it("divide - round", () => {
-    const base = LazyBase.lazy(1.5)
-      .divide(2)
-      .round(2);
-    expect(base.value()).toBe(0.75);
-  });
-
-  it("divide - floor", () => {
-    const base = LazyBase.lazy(1.5)
-      .divide(2)
-      .floor(1);
-    expect(base.value()).toBe(0.7);
-  });
-  it("divide - ceil", () => {
-    const base = LazyBase.lazy(1.5)
-      .divide(2)
-      .ceil(1);
-    expect(base.value()).toBe(0.8);
-  });
-  it("default", () => {
-    const base = LazyBase.lazy(1.5)
-      .divide(0)
-      .default(99);
-    expect(base.value()).toBe(99);
-  });
-
-  it("do", () => {
-    const base = LazyBase.lazy({ num: 1.5 })
-      .do((x: { num: number }) => x.num)
-      .multiply(2);
-    expect(base.value()).toBe(3);
+  it("stream with init value", () => {
+    const base1 = LazyBase.lazy(1);
+    const base2 = LazyBase.lazy(4);
+    const stream1 = LazyBase.stream(base1).add(base2);
+    expect(stream1.value()).toBe(5);
   });
 });

tests/unit/simple.spec.ts

@@ -0,0 +1,78 @@
+import { LazyBase } from "../../src/main";
+
+describe("simple class", () => {
+  it("add", () => {
+    const base = LazyBase.lazy(1).add(4);
+    expect(base.value()).toBe(5);
+  });
+
+  it("subtract", () => {
+    const base = LazyBase.lazy(1).subtract(4);
+    expect(base.value()).toBe(-3);
+  });
+
+  it("multiply", () => {
+    const base = LazyBase.lazy(1).multiply(4);
+    expect(base.value()).toBe(4);
+  });
+  it("multiply - float", () => {
+    const base = LazyBase.lazy(1.5).multiply(4);
+    expect(base.value()).toBe(6);
+  });
+
+  it("divide - round", () => {
+    const base = LazyBase.lazy(1.5)
+      .divide(2)
+      .round(2);
+    expect(base.value()).toBe(0.75);
+  });
+
+  it("divide - floor", () => {
+    const base = LazyBase.lazy(1.5)
+      .divide(2)
+      .floor(1);
+    expect(base.value()).toBe(0.7);
+  });
+  it("divide - ceil", () => {
+    const base = LazyBase.lazy(1.5)
+      .divide(2)
+      .ceil(1);
+    expect(base.value()).toBe(0.8);
+  });
+
+  it("precision - invalid", () => {
+    const base = LazyBase.lazy(1.5)
+      .divide(0)
+      .ceil(1)
+      .default("m");
+    expect(base.value()).toBe("m");
+  });
+
+  it("precision - minus", () => {
+    const base = LazyBase.lazy(1.5)
+      .divide(1)
+      .ceil(-2)
+      .default("m");
+    expect(base.value()).toBe(100);
+  });
+  it("precision - null", () => {
+    const base = LazyBase.lazy(1.5)
+      .divide(1)
+      .ceil()
+      .default("m");
+    expect(base.value()).toBe(2);
+  });
+  it("default", () => {
+    const base = LazyBase.lazy(1.5)
+      .divide(0)
+      .default(99);
+    expect(base.value()).toBe(99);
+  });
+
+  it("do", () => {
+    const base = LazyBase.lazy({ num: 1.5 })
+      .do((x: { num: number }) => x.num)
+      .multiply(2);
+    expect(base.value()).toBe(3);
+  });
+});