Initial import with skill sheet working

node_modules/abstract-level/test/self/defer-test.js

@@ -0,0 +1,90 @@
+'use strict'
+
+const test = require('tape')
+const { mockLevel } = require('../util')
+
+test('defer() requires valid function argument', function (t) {
+  t.plan(7)
+
+  const db = mockLevel()
+
+  for (const invalid of [123, true, false, null, undefined, {}]) {
+    try {
+      db.defer(invalid)
+    } catch (err) {
+      t.is(err.message, 'The first argument must be a function')
+    }
+  }
+
+  db.close(t.ifError.bind(t))
+})
+
+test('defer() custom operation', function (t) {
+  t.plan(6)
+
+  const db = mockLevel({
+    custom (arg, callback) {
+      if (this.status === 'opening') {
+        t.is(arg, 123)
+        this.defer(() => this.custom(456, callback))
+      } else {
+        t.is(db.status, 'open')
+        t.is(arg, 456)
+        this.nextTick(callback, null, 987)
+      }
+    }
+  })
+
+  db.custom(123, function (err, result) {
+    t.ifError(err, 'no custom() error')
+    t.is(result, 987, 'result ok')
+
+    db.close(t.ifError.bind(t))
+  })
+})
+
+test('defer() custom operation with failed open', function (t) {
+  t.plan(4)
+
+  const db = mockLevel({
+    _open (options, callback) {
+      t.pass('opened')
+      this.nextTick(callback, new Error('_open error'))
+    },
+    custom (arg, callback) {
+      if (this.status === 'opening') {
+        this.defer(() => this.custom(arg, callback))
+      } else {
+        t.is(db.status, 'closed')
+        this.nextTick(callback, new Error('Database is not open (x)'))
+      }
+    }
+  })
+
+  db.custom(123, function (err, result) {
+    t.is(err && err.message, 'Database is not open (x)')
+    t.is(result, undefined, 'result ok')
+  })
+})
+
+test('defer() can drop custom synchronous operation', function (t) {
+  t.plan(3)
+
+  const db = mockLevel({
+    _open (options, callback) {
+      t.pass('opened')
+      this.nextTick(callback, new Error('_open error'))
+    },
+    custom (arg) {
+      if (this.status === 'opening') {
+        this.defer(() => this.custom(arg * 2))
+      } else {
+        // Handling other states is a userland responsibility
+        t.is(db.status, 'closed')
+        t.is(arg, 246)
+      }
+    }
+  })
+
+  db.custom(123)
+})