✅ add failing tests for maybeError() and closed db

test/.gitignore

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+_levelup_test_db_61

test/maybe-error-test.js

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+/* Copyright (c) 2012-2017 LevelUP contributors
+ * See list at <https://github.com/level/levelup#contributing>
+ * MIT License <https://github.com/level/levelup/blob/master/LICENSE.md>
+ */
+
+var common = require('./common')
+var assert = require('referee').assert
+var refute = require('referee').refute
+var buster = require('bustermove')
+
+buster.testCase('maybeError called sync', {
+  'setUp': common.commonSetUp,
+  'tearDown': common.commonTearDown,
+
+  'put()': function (done) {
+    this.openTestDatabase(function (db) {
+      db.close(function () {
+        assert.isTrue(db.isClosed(), 'db is closed')
+        let sync = false
+        db.put('key', 'value', {}, function (err) {
+          sync = true
+          assert(err)
+          assert.equals(err.message, 'Database is not open')
+        })
+        assert.isFalse(sync, '.put cb called synchronously')
+        done()
+      })
+    })
+  },
+
+  'get()': function (done) {
+    this.openTestDatabase(function (db) {
+      db.put('key', 'value', {}, function (err) {
+        refute(err)
+        db.close(function () {
+          assert.isTrue(db.isClosed(), 'db is closed')
+          let sync = false
+          db.get('key', {}, function (err, value) {
+            sync = true
+            assert(err)
+            assert.equals(err.message, 'Database is not open')
+          })
+          assert.isFalse(sync, '.get cb called synchronously')
+          done()
+        })
+      })
+    })
+  },
+
+  'del()': function (done) {
+    this.openTestDatabase(function (db) {
+      db.put('key', 'value', {}, function (err) {
+        refute(err)
+        db.close(function () {
+          assert.isTrue(db.isClosed(), 'db is closed')
+          let sync = false
+          db.del('key', {}, function (err) {
+            sync = true
+            assert(err)
+            assert.equals(err.message, 'Database is not open')
+          })
+          assert.isFalse(sync, '.del cb called synchronously')
+          done()
+        })
+      })
+    })
+  },
+
+  'batch()': function (done) {
+    this.openTestDatabase(function (db) {
+      db.close(function () {
+        assert.isTrue(db.isClosed(), 'db is closed')
+        let sync = false
+        db.batch([{ type: 'put', key: 'key' }], {}, function (err) {
+          sync = true
+          assert(err)
+          assert.equals(err.message, 'Database is not open')
+        })
+        assert.isFalse(sync, '.batch cb called synchronously')
+        done()
+      })
+    })
+  }
+})