New: no-assert-logical-expression rule (fixes #50)

README.md

@@ -15,6 +15,7 @@ Below is the list of rules available in this plugin.
 * [literal-compare-order](./docs/rules/literal-compare-order.md)
 * [no-arrow-tests](./docs/rules/no-arrow-tests.md)
 * [no-assert-equal](./docs/rules/no-assert-equal.md)
+* [no-assert-logical-expression](./docs/rules/no-assert-logical-expression.md)
 * [no-async-in-loops](./docs/rules/no-async-in-loops.md)
 * [no-async-test](./docs/rules/no-async-test.md)
 * [no-commented-tests](./docs/rules/no-commented-tests.md)

docs/rules/no-assert-logical-expression.md

@@ -0,0 +1,32 @@
+# Forbid binary logical expressions in assert arguments (no-assert-logical-expression)
+
+Generally, it is not a good idea to use logical expressions as assertion arguments. Logical-and assertions can be broken down into multiple assertions, while logical-or assertions may be indicative of uncertainty or nondeterminism in a test.
+
+## Rule Details
+
+The following patterns are considered warnings:
+
+```js
+
+assert.ok(foo && bar);
+
+assert.ok(foo || bar);
+
+```
+
+The following patterns are not warnings:
+
+```js
+
+// Multiple assertions for logical-and cases
+assert.ok(foo);
+assert.ok(bar);
+
+// More deterministic test expectation: maybe only foo should be true here
+assert.ok(foo);
+
+```
+
+## When Not To Use It
+
+This rule can be safely disabled if you do not care about the quality of test assertions and the determinism of tests.

index.js

@@ -6,6 +6,7 @@ module.exports = {
         "literal-compare-order": require("./lib/rules/literal-compare-order"),
         "no-arrow-tests": require("./lib/rules/no-arrow-tests"),
         "no-assert-equal": require("./lib/rules/no-assert-equal"),
+        "no-assert-logical-expression": require("./lib/rules/no-assert-logical-expression"),
         "no-async-in-loops": require("./lib/rules/no-async-in-loops"),
         "no-async-test": require("./lib/rules/no-async-test"),
         "no-commented-tests": require("./lib/rules/no-commented-tests"),

lib/rules/no-assert-logical-expression.js

@@ -0,0 +1,84 @@
+/**
+ * @fileoverview forbid binary logical expressions in assert arguments
+ * @author Kevin Partington
+ */
+"use strict";
+
+//------------------------------------------------------------------------------
+// Requirements
+//------------------------------------------------------------------------------
+
+var utils = require("../utils");
+
+//------------------------------------------------------------------------------
+// Rule Definition
+//------------------------------------------------------------------------------
+
+module.exports = {
+    meta: {
+        docs: {
+            description: "forbid binary logical expressions in assert arguments",
+            category: "Best Practices",
+            recommended: false
+        },
+        fixable: null,
+        schema: []
+    },
+
+    create: function (context) {
+        var testStack = [],
+            MESSAGE = "Do not use '{{operator}}' in assertion arguments.";
+
+        //----------------------------------------------------------------------
+        // Helpers
+        //----------------------------------------------------------------------
+
+        function checkAndReport(argNodes) {
+            argNodes.forEach(function (arg) {
+                if (arg.type === "LogicalExpression") {
+                    context.report({
+                        node: arg,
+                        message: MESSAGE,
+                        data: {
+                            operator: arg.operator
+                        }
+                    });
+                }
+            });
+        }
+
+        function getAssertVar() {
+            var result = null;
+
+            if (testStack.length) {
+                result = testStack[testStack.length - 1].assertContextVar;
+            }
+
+            return result;
+        }
+
+        //----------------------------------------------------------------------
+        // Public
+        //----------------------------------------------------------------------
+
+        return {
+
+            "CallExpression": function (node) {
+                if (utils.isTest(node.callee)) {
+                    testStack.push({
+                        assertContextVar: utils.getAssertContextNameForTest(node.arguments)
+                    });
+                } else if (utils.isAssertion(node.callee, getAssertVar())) {
+                    checkAndReport(node.arguments);
+                }
+            },
+
+            "CallExpression:exit": function (node) {
+                if (utils.isTest(node.callee)) {
+                    testStack.pop();
+                }
+            }
+
+        };
+    }
+};