add stream folder with scan and scan-merge

stream/tests/test-stream.js

@@ -0,0 +1,90 @@
+'use strict'
+
+var o = require('../../ospec/ospec')
+
+o.spec('stream', function () {
+  var prop
+
+  o.beforeEach(function () {
+    prop = require('../../stream')
+  })
+
+  o.spec('scan', function () {
+    var scan
+
+    o.beforeEach(function () {
+      scan = require('../scan')
+    })
+
+    o('defaults to seed', function () {
+      var parent = prop()
+      var child = scan(function (out, p) {
+        return out - p
+      }, 123, parent)
+      o(child()).equals(123)
+    })
+
+    o('accumulates values as expected', function () {
+      var parent = prop()
+      var child = scan(function (arr, p) {
+        return arr.concat(p)
+      }, [], parent)
+
+      parent(7)
+      parent('11')
+      parent(undefined)
+      parent({ a: 1 })
+      var result = child()
+
+      // deepEquals fails on arrays?
+      o(result[0]).equals(7)
+      o(result[1]).equals('11')
+      o(result[2]).equals(undefined)
+      o(result[3]).deepEquals({ a: 1 })
+    })
+  })
+
+  o.spec('scanMerge', function () {
+    var scanMerge
+
+    o.beforeEach(function () {
+      scanMerge = require('../scan-merge')
+    })
+
+    o('defaults to seed', function () {
+      var parent1 = prop()
+      var parent2 = prop()
+
+      var child = scanMerge([
+        [parent1, function (out, p1) {
+          return out + p1
+        }],
+        [parent2, function (out, p2) {
+          return out + p2
+        }]
+      ], -10)
+
+      o(child()).equals(-10)
+    })
+
+    o('accumulates as expected', function () {
+      var parent1 = prop()
+      var parent2 = prop()
+
+      var child = scanMerge([
+        [parent1, function (out, p1) {
+          return out + p1
+        }],
+        [parent2, function (out, p2) {
+          return out + p2 + p2
+        }]
+      ], 'a')
+
+      parent1('b')
+      parent2('c')
+      parent1('b')
+
+      o(child()).equals('abccb')
+    })
+  })
+})