style: rename target argument to subject

Most assertions use the term "target" to refer to the object under
test, but a few assertions also had a `target` argument, resulting in
an overloaded term that was difficult to document. This commit
renames every `target` argument to `subject`.

lib/chai/core/assertions.js

@@ -2153,14 +2153,14 @@ module.exports = function (chai, _) {
    * @name change
    * @alias changes
    * @alias Change
-   * @param {String} target
+   * @param {String} subject
    * @param {String} property name _optional_
    * @param {String} message _optional_
    * @namespace BDD
    * @api public
    */
 
-  function assertChanges (target, prop, msg) {
+  function assertChanges (subject, prop, msg) {
     if (msg) flag(this, 'message', msg);
     var fn = flag(this, 'object')
       , flagMsg = flag(this, 'message')
@@ -2169,16 +2169,16 @@ module.exports = function (chai, _) {
 
     var initial;
     if (!prop) {
-      new Assertion(target, flagMsg, ssfi, true).is.a('function');
-      initial = target();
+      new Assertion(subject, flagMsg, ssfi, true).is.a('function');
+      initial = subject();
     } else {
-      new Assertion(target, flagMsg, ssfi, true).to.have.property(prop);
-      initial = target[prop];
+      new Assertion(subject, flagMsg, ssfi, true).to.have.property(prop);
+      initial = subject[prop];
     }
 
     fn();
 
-    var final = prop === undefined || prop === null ? target() : target[prop];
+    var final = prop === undefined || prop === null ? subject() : subject[prop];
     var msgObj = prop === undefined || prop === null ? initial : '.' + prop;
 
     // This gets flagged because of the .by(delta) assertion
@@ -2199,7 +2199,7 @@ module.exports = function (chai, _) {
   Assertion.addMethod('changes', assertChanges);
 
   /**
-   * ### .increase(target[, property[, message]])
+   * ### .increase(subject[, property[, message]])
    *
    * Asserts that a function increases a numeric object property.
    *
@@ -2217,14 +2217,14 @@ module.exports = function (chai, _) {
    * @name increase
    * @alias increases
    * @alias Increase
-   * @param {String|Function} target
+   * @param {String|Function} subject
    * @param {String} property name _optional_
    * @param {String} message _optional_
    * @namespace BDD
    * @api public
    */
 
-  function assertIncreases (target, prop, msg) {
+  function assertIncreases (subject, prop, msg) {
     if (msg) flag(this, 'message', msg);
     var fn = flag(this, 'object')
       , flagMsg = flag(this, 'message')
@@ -2233,19 +2233,19 @@ module.exports = function (chai, _) {
 
     var initial;
     if (!prop) {
-      new Assertion(target, flagMsg, ssfi, true).is.a('function');
-      initial = target();
+      new Assertion(subject, flagMsg, ssfi, true).is.a('function');
+      initial = subject();
     } else {
-      new Assertion(target, flagMsg, ssfi, true).to.have.property(prop);
-      initial = target[prop];
+      new Assertion(subject, flagMsg, ssfi, true).to.have.property(prop);
+      initial = subject[prop];
     }
 
     // Make sure that the target is a number
     new Assertion(initial, flagMsg, ssfi, true).is.a('number');
 
     fn();
 
-    var final = prop === undefined || prop === null ? target() : target[prop];
+    var final = prop === undefined || prop === null ? subject() : subject[prop];
     var msgObj = prop === undefined || prop === null ? initial : '.' + prop;
 
     flag(this, 'deltaMsgObj', msgObj);
@@ -2265,7 +2265,7 @@ module.exports = function (chai, _) {
   Assertion.addMethod('increases', assertIncreases);
 
   /**
-   * ### .decrease(target[, property[, message]])
+   * ### .decrease(subject[, property[, message]])
    *
    * Asserts that a function decreases a numeric object property.
    *
@@ -2283,14 +2283,14 @@ module.exports = function (chai, _) {
    * @name decrease
    * @alias decreases
    * @alias Decrease
-   * @param {String|Function} target
+   * @param {String|Function} subject
    * @param {String} property name _optional_
    * @param {String} message _optional_
    * @namespace BDD
    * @api public
    */
 
-  function assertDecreases (target, prop, msg) {
+  function assertDecreases (subject, prop, msg) {
     if (msg) flag(this, 'message', msg);
     var fn = flag(this, 'object')
       , flagMsg = flag(this, 'message')
@@ -2299,19 +2299,19 @@ module.exports = function (chai, _) {
 
     var initial;
     if (!prop) {
-      new Assertion(target, flagMsg, ssfi, true).is.a('function');
-      initial = target();
+      new Assertion(subject, flagMsg, ssfi, true).is.a('function');
+      initial = subject();
     } else {
-      new Assertion(target, flagMsg, ssfi, true).to.have.property(prop);
-      initial = target[prop];
+      new Assertion(subject, flagMsg, ssfi, true).to.have.property(prop);
+      initial = subject[prop];
     }
 
     // Make sure that the target is a number
     new Assertion(initial, flagMsg, ssfi, true).is.a('number');
 
     fn();
 
-    var final = prop === undefined || prop === null ? target() : target[prop];
+    var final = prop === undefined || prop === null ? subject() : subject[prop];
     var msgObj = prop === undefined || prop === null ? initial : '.' + prop;
 
     flag(this, 'deltaMsgObj', msgObj);