Started the kotlin track

This commit is contained in:
Brian Buller 2018-06-21 08:54:16 -05:00
parent ce5ea92f79
commit c0f0c379fa
446 changed files with 3085 additions and 574 deletions

148
go/robot-simulator/robot.go Normal file
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@ -0,0 +1,148 @@
package robot
import "fmt"
const testVersion = 3
// Stuff added for step 1
const (
N = iota
E
S
W
ErrDir
)
func Advance() {
switch Step1Robot.Dir {
case N:
Step1Robot.Y++
case E:
Step1Robot.X++
case S:
Step1Robot.Y--
case W:
Step1Robot.X--
}
}
func Left() {
switch Step1Robot.Dir {
case N:
Step1Robot.Dir = W
case E:
Step1Robot.Dir = N
case S:
Step1Robot.Dir = E
case W:
Step1Robot.Dir = S
}
}
func Right() {
switch Step1Robot.Dir {
case N:
Step1Robot.Dir = E
case E:
Step1Robot.Dir = S
case S:
Step1Robot.Dir = W
case W:
Step1Robot.Dir = N
}
}
func (d Dir) String() string {
switch d {
case N:
return "N"
case E:
return "E"
case S:
return "S"
default:
return "W"
}
}
// Stuff added for step 2
type Action byte
func StartRobot(cmd chan Command, act chan Action) {
fmt.Println("Starting Robot")
for {
fmt.Println("Waiting for command")
j, more := <-cmd
fmt.Println("Received a Command:", j)
if more {
// Received a command, try to act in the room
act <- Action(j)
}
}
fmt.Println("Robot Done")
}
func Room(extent Rect, robot Step2Robot, act chan Action, rep chan Step2Robot) {
fmt.Println("Starting Room")
for {
j, more := <-act
if more {
// Received an action, try to perform it
if j == 'R' { // Turn Right
switch robot.Dir {
case N:
robot.Dir = E
case E:
robot.Dir = S
case S:
robot.Dir = W
case W:
robot.Dir = N
}
} else if j == 'L' { // Turn Left
switch robot.Dir {
case N:
robot.Dir = W
case E:
robot.Dir = N
case S:
robot.Dir = E
case W:
robot.Dir = S
}
} else if j == 'A' { // Advance
switch robot.Dir {
case N:
if robot.Pos.Northing < extent.Max.Northing {
robot.Pos.Northing++
} else {
fmt.Println("Hit North Wall")
}
case E:
if robot.Pos.Easting < extent.Max.Easting {
robot.Pos.Easting++
} else {
fmt.Println("Hit East Wall")
}
case S:
if robot.Pos.Northing > extent.Min.Northing {
robot.Pos.Northing--
} else {
fmt.Println("Hit South Wall")
}
case W:
if robot.Pos.Easting > extent.Min.Easting {
robot.Pos.Easting--
} else {
fmt.Println("Hit West Wall")
}
}
}
} else {
// Done, report back
rep <- robot
}
}
close(rep)
fmt.Println("Room Done")
}

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@ -2,7 +2,10 @@
package robot
import "testing"
import (
"fmt"
"testing"
)
// For step 1 you implement robot movements, but it's not much of a simulation.
// For example where in the source code is "the robot"? Where is "the grid"?
@ -72,7 +75,9 @@ func TestStep2(t *testing.T) {
rep := make(chan Step2Robot)
go StartRobot(cmd, act)
go Room(Rect{Pos{1, 1}, Pos{2, 2}}, test2[0].Step2Robot, act, rep)
fmt.Println("Starting Tests")
for j := 1; j < i; j++ {
fmt.Println("Channeling: ", test2[j])
cmd <- test2[j].Command
}
close(cmd)

54
go/space-age/README.md Normal file
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@ -0,0 +1,54 @@
# Space Age
Given an age in seconds, calculate how old someone would be on:
- Earth: orbital period 365.25 Earth days, or 31557600 seconds
- Mercury: orbital period 0.2408467 Earth years
- Venus: orbital period 0.61519726 Earth years
- Mars: orbital period 1.8808158 Earth years
- Jupiter: orbital period 11.862615 Earth years
- Saturn: orbital period 29.447498 Earth years
- Uranus: orbital period 84.016846 Earth years
- Neptune: orbital period 164.79132 Earth years
So if you were told someone were 1,000,000,000 seconds old, you should
be able to say that they're 31.69 Earth-years old.
If you're wondering why Pluto didn't make the cut, go watch [this
youtube video](http://www.youtube.com/watch?v=Z_2gbGXzFbs).
## No Stub
This may be the first Go track exercise you encounter without a stub: a
pre-existing `space_age.go` file for your solution. You may not see stubs in
the future and should begin to get comfortable with creating your own Go files
for your solutions.
One way to figure out what the function signature(s) you would need is to look
at the corresponding \*\_test.go file. It will show you what the package level
functions(s) should be that the test will use to verify the solution.
## Running the tests
To run the tests run the command `go test` from within the exercise directory.
If the test suite contains benchmarks, you can run these with the `-bench`
flag:
go test -bench .
Keep in mind that each reviewer will run benchmarks on a different machine, with
different specs, so the results from these benchmark tests may vary.
## Further information
For more detailed information about the Go track, including how to get help if
you're having trouble, please visit the exercism.io [Go language page](http://exercism.io/languages/go/about).
## Source
Partially inspired by Chapter 1 in Chris Pine's online Learn to Program tutorial. [http://pine.fm/LearnToProgram/?Chapter=01](http://pine.fm/LearnToProgram/?Chapter=01)
## Submitting Incomplete Solutions
It's possible to submit an incomplete solution so you can see how others have completed the exercise.

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@ -0,0 +1,61 @@
package space
// Source: exercism/problem-specifications
// Commit: 8d4df79 space-age: Apply new "input" policy
// Problem Specifications Version: 1.1.0
var testCases = []struct {
description string
planet Planet
seconds float64
expected float64
}{
{
description: "age on Earth",
planet: "Earth",
seconds: 1000000000,
expected: 31.69,
},
{
description: "age on Mercury",
planet: "Mercury",
seconds: 2134835688,
expected: 280.88,
},
{
description: "age on Venus",
planet: "Venus",
seconds: 189839836,
expected: 9.78,
},
{
description: "age on Mars",
planet: "Mars",
seconds: 2329871239,
expected: 39.25,
},
{
description: "age on Jupiter",
planet: "Jupiter",
seconds: 901876382,
expected: 2.41,
},
{
description: "age on Saturn",
planet: "Saturn",
seconds: 3000000000,
expected: 3.23,
},
{
description: "age on Uranus",
planet: "Uranus",
seconds: 3210123456,
expected: 1.21,
},
{
description: "age on Neptune",
planet: "Neptune",
seconds: 8210123456,
expected: 1.58,
},
}

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@ -0,0 +1,25 @@
package space
import (
"math"
"testing"
)
func TestAge(t *testing.T) {
const precision = 0.01
for _, tc := range testCases {
actual := Age(tc.seconds, tc.planet)
if math.IsNaN(actual) || math.Abs(actual-tc.expected) > precision {
t.Fatalf("FAIL: %s\nExpected: %#v\nActual: %#v", tc.description, tc.expected, actual)
}
t.Logf("PASS: %s", tc.description)
}
}
func BenchmarkAge(b *testing.B) {
for i := 0; i < b.N; i++ {
for _, tc := range testCases {
Age(tc.seconds, tc.planet)
}
}
}

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@ -0,0 +1,2 @@
#Thu Jun 21 08:10:45 CDT 2018
gradle.version=4.8

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@ -1,50 +0,0 @@
----
# Quick Start Guide
This guide picks-up where [Running the Tests (in Kotlin)](http://exercism.io/languages/kotlin/tests)
left off. If you haven't reviewed those instructions, do so now.
Need more information? A **step-by-step tutorial** is available in this directory at TUTORIAL.md or you can read
the [HTML version](https://github.com/exercism/kotlin/blob/master/exercises/hello-world/TUTORIAL.md).
The following instructions work equally well on Windows, Mac OS X and Linux.
## Solve "Hello World"
Try writing a solution that passes one test at a time, running Gradle each time:
```
$ gradle test
```
## Iterate through the tests
After your first test passes, remove the `@Ignore` from the next test, and iterate on your solution,
testing after each change.
## All the tests pass? Submit your solution!
With a working solution that we've reviewed, we're ready to submit it to
exercism.io.
```
$ exercism submit src/main/kotlin/HelloWorld.kt
```
## Next Steps
From here, there are a number of paths you can take.
1. Move on to the next exercise
2. Review (and comment on) others' submissions to this exercise
3. Submit another iteration
4. Contribute to Exercism
We sincerely hope you learn and enjoy being part of this community. If at any time you need assistance
do not hesitate to ask for help:
http://exercism.io/languages/kotlin/help
Cheers!

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@ -1,48 +1,30 @@
# Hello World
Write a function that greets the user by name, or by saying "Hello, World!" if no name is given.
The classical introductory exercise. Just say "Hello, World!".
["Hello, World!"](http://en.wikipedia.org/wiki/%22Hello,_world!%22_program) is the traditional first program for beginning programming in a new language.
["Hello, World!"](http://en.wikipedia.org/wiki/%22Hello,_world!%22_program) is
the traditional first program for beginning programming in a new language
or environment.
**Note:** You can skip this exercise by running:
The objectives are simple:
exercism skip $LANGUAGE hello-world
- Write a function that returns the string "Hello, World!".
- Run the test suite and make sure that it succeeds.
- Submit your solution and check it at the website.
## Specification
If everything goes well, you will be ready to fetch your first real exercise.
Write a `Hello World!` function that can greet someone given their name.
The function should return the appropriate greeting.
Since this is your first Kotlin exercise, we've included a detailed TUTORIAL.md
file that guides you through your solution. Check it out for tips and
assistance!
For an input of "Alice", the response should be "Hello, Alice!".
If a name is not given, the response should be "Hello, World!"
## Test-Driven Development
As programmers mature, they eventually want to test their code.
Here at Exercism we simulate [Test-Driven Development](http://en.wikipedia.org/wiki/Test-driven_development) (TDD), where you write your tests before writing any functionality. The simulation comes in the form of a pre-written test suite, which will signal that you have solved the problem.
It will also provide you with a safety net to explore other solutions without breaking the functionality.
### A typical TDD workflow on Exercism:
1. Run the test file and pick one test that's failing.
2. Write some code to fix the test you picked.
3. Re-run the tests to confirm the test is now passing.
4. Repeat from step 1.
5. Submit your solution (`exercism submit /path/to/file`)
## Instructions
Submissions are encouraged to be general, within reason. Having said that, it's also important not to over-engineer a solution.
It's important to remember that the goal is to make code as expressive and readable as we can. However, solutions to the hello-world exercise will not be reviewed by a person, but by rikki- the robot, who will offer an encouraging word.
## Source
This is an exercise to introduce users to using Exercism [http://en.wikipedia.org/wiki/%22Hello,_world!%22_program](http://en.wikipedia.org/wiki/%22Hello,_world!%22_program)
## Submitting Incomplete Problems
## Submitting Incomplete Solutions
It's possible to submit an incomplete solution so you can see how others have completed the exercise.

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@ -1,22 +1,15 @@
NOTE: You can also view the HTML version of this file here:
https://github.com/exercism/kotlin/blob/master/exercises/hello-world/TUTORIAL.md
* [Introduction](#introduction)
* [Exercise Structure](#exercise-structure)
* [Solving "Hello, World!"](#solving-hello-world)
* [Reading Gradle output](#reading-gradle-output)
* [Fixing the first failing test](#fixing-the-first-failing-test)
* [Enabling and fixing the second test](#enabling-and-fixing-the-second-test)
* [Enabling and fixing the third test](#enabling-and-fixing-the-third-test)
* [Enabling the last test](#enabling-the-last-test)
* [Refactoring](#refactoring)
* [Submitting your first iteration](#submitting-your-first-iteration)
* [Next Steps](#next-steps)
* [Review (and comment on) others' submissions to this exercise](#review-and-comment-on-others-submissions-to-this-exercise)
* [Extend an exercise](#extend-an-exercise)
* [Contribute to Exercism](#contribute-to-exercism)
----
# Solving "Hello, World!"
# Introduction
Welcome to the first exercise on the Kotlin track!
@ -26,7 +19,7 @@ Each exercise comes with a set of tests. The first pass through the
exercise is about getting all of the tests to pass, one at a time.
If you have not installed the Java Development Kit and Gradle, you must do
so now. For help with this, see: http://exercism.io/languages/kotlin/installing
so now. For help with this, see: http://exercism.io/languages/kotlin/installation
----
@ -35,7 +28,22 @@ left off. If you haven't reviewed those instructions, do so now.
The following instructions work equally well on Windows, Mac OS X and Linux.
## Reading Gradle output
# Exercise Structure
When you fetch a new Kotlin exercise, you will receive:
* __one or more test files__ (always). These live in the `src/test/kotlin`
directory and define a set of tests that our solution must satisfy before we
can safely declare that it is working.
* __one or more starter files__ (initially). If provided, these live in the
`src/main/kotlin` directory and define shells of the classes you will need
in order to solve the current problem.
# Solving "Hello World!"
## Step 1: Run the tests against the starter solution
Use Gradle to run the tests:
@ -84,19 +92,14 @@ running the task you asked it to: executing the tests against the solution.
```
:test
HelloWorldTest > helloSampleName SKIPPED
HelloWorldTest > helloBlankName SKIPPED
HelloWorldTest > helloNoName FAILED
HelloWorldTest > helloWorldTest FAILED
org.junit.ComparisonFailure: expected:<[Hello, World!]> but was:<[]>
at org.junit.Assert.assertEquals(Assert.java:115)
at org.junit.Assert.assertEquals(Assert.java:144)
at HelloWorldTest.helloNoName(HelloWorldTest.kt:10)
HelloWorldTest > helloAnotherSampleName SKIPPED
4 tests completed, 1 failed, 3 skipped
1 test completed, 1 failed
:test FAILED
FAILURE: Build failed with an exception.
@ -113,19 +116,19 @@ BUILD FAILED
Total time: 7.473 secs
```
Seeing the word "fail" NINE TIMES might give you the impression you've done
Seeing the word "fail" might give you the impression you've done
something horribly wrong! You haven't. It's a whole lot of noise over
a single test not passing.
Let's focus in on the important bits:
```
HelloWorldTest > helloNoName FAILED
HelloWorldTest > helloWorldTest FAILED
org.junit.ComparisonFailure: expected:<[Hello, World!]> but was:<[]>
```
...is read: "Within the test class named `HelloWorldTest`, the test method
`helloNoName` did not pass because the solution did not satisfy an
`helloWorldTest` did not pass because the solution did not satisfy an
assertion. Apparently, we expected to see the string 'Hello, World!' but
a blank string was returned instead.
@ -133,7 +136,7 @@ The last line of the stack trace tells us exactly where this unsatisfied
assertion lives:
```
at HelloWorldTest.helloNoName(HelloWorldTest.kt:10)
at HelloWorldTest.helloWorldTest(HelloWorldTest.kt:10)
```
Looks like the scene of the crime is on line 10 in the test file.
@ -145,25 +148,22 @@ Knowing these two facts,
we can turn this failure into success.
## Fixing the first failing test
## Step 2: Fix the Test!
In your favorite text editor, open `src/test/kotlin/HelloWorldTest.kt`
and go to line 10.
```kotlin
assertEquals("Hello, World!", hello(""))
assertEquals("Hello, World!", hello())
```
The test is expecting that `hello()`, when given an empty string (`""`),
returns "Hello, World!". Instead, `hello()` is returning `""`.
The test is expecting that `hello()`, returns "Hello, World!". Instead, `hello()` is returning `""`.
Let's fix that.
Open `src/main/kotlin/HelloWorld.kt`.
```kotlin
fun hello(name: String = ""): String {
fun hello(): String {
return ""
}
```
@ -171,7 +171,7 @@ fun hello(name: String = ""): String {
Let's change that to return the expected string:
```kotlin
fun hello(name: String = ""): String {
fun hello(): String {
return "Hello, World!"
}
```
@ -181,7 +181,6 @@ Save the file and run the tests again:
```
$ gradle test
:compileKotlin
w: /Users/jtigger/exercism/exercises/kotlin/hello-world/src/main/kotlin/HelloWorld.kt: (1, 11): Parameter 'name' is never used
:compileJava UP-TO-DATE
:copyMainKotlinClasses
:processResources UP-TO-DATE
@ -193,419 +192,18 @@ w: /Users/jtigger/exercism/exercises/kotlin/hello-world/src/main/kotlin/HelloWor
:testClasses UP-TO-DATE
:test
HelloWorldTest > helloSampleName SKIPPED
HelloWorldTest > helloBlankName SKIPPED
HelloWorldTest > helloNoName PASSED
HelloWorldTest > helloAnotherSampleName SKIPPED
HelloWorldTest > helloWorldTest PASSED
BUILD SUCCESSFUL
Total time: 7.318 secs
```
"BUILD SUCCESSFUL"! Woohoo! :) You can see that `helloNoName()` test is
"BUILD SUCCESSFUL"! Woohoo! :) You can see that `helloWorldTest()` test is
now passing.
We still see the warning about `name` not being used; we'll get to that
next.
With one win under our belt, we can turn our focus to some other messages
that we've been ignoring: the lines ending in "`SKIPPED`".
Each test suite contains a series of tests, all of which have been marked
to be skipped/ignored except the first one. We did this to help you focus
on getting one test running at a time.
Let's tackle the next test...
## Enabling and fixing the second test
Right now, that second test is being skipped/ignored. Let's enable it.
(Re)open `src/test/kotlin/HelloWorldTest.kt` and find the second test:
```kotlin
@Test
@Ignore
fun helloSampleName() {
assertEquals("Hello, Alice!", hello("Alice"))
}
```
When the JUnit test runner sees that `@Ignore` annotation on the test
method, it knows to skip over that test. Remove that line:
```kotlin
@Test
fun helloSampleName() {
assertEquals("Hello, Alice!", hello("Alice"))
}
```
Now, when you run the tests, both tests run:
```
$ gradle test
:test
HelloWorldTest > helloSampleName FAILED
org.junit.ComparisonFailure: expected:<Hello, [Alice]!> but was:<Hello, [World]!>
at org.junit.Assert.assertEquals(Assert.java:115)
at org.junit.Assert.assertEquals(Assert.java:144)
at HelloWorldTest.helloSampleName(HelloWorldTest.kt:15)
HelloWorldTest > helloBlankName SKIPPED
HelloWorldTest > helloNoName PASSED
HelloWorldTest > helloAnotherSampleName SKIPPED
4 tests completed, 1 failed, 2 skipped
```
The first test, `helloNoName()` continues to pass. We see that
`helloSampleName` -- the test we just un-`@Ignore`'d -- is now running and
failing. Yay, failing test! In fact, the "failure" message is just
describing the difference between what the program does now and what it
should do for us to call it "done."
Right now, we've hardcoded the greeting. Enabling this second test has
unleashed a new expectation: that our program incorporate a name given
into that greeting. When given the name "`Alice`", that's who should be
greeted instead of "`World`".
(Re)open `src/main/kotlin/HelloWorld.kt`.
```kotlin
fun hello(name: String = ""): String {
return "Hello, World!"
}
```
While `hello()` does accept a reference to a string named `name`, it is not
using it in the output. Let's change that:
```kotlin
fun hello(name: String = ""): String {
return "Hello, $name!"
}
```
_(Kotlin allows you to embed expressions within strings, a feature known as
string interpolation. For more about this feature, see
https://kotlinlang.org/docs/reference/basic-types.html#string-templates )_
... and rerun the tests ...
```
$ gradle test
:test
HelloWorldTest > helloSampleName PASSED
HelloWorldTest > helloBlankName SKIPPED
HelloWorldTest > helloNoName FAILED
org.junit.ComparisonFailure: expected:<Hello, [World]!> but was:<Hello, []!>
at org.junit.Assert.assertEquals(Assert.java:115)
at org.junit.Assert.assertEquals(Assert.java:144)
at HelloWorldTest.helloNoName(HelloWorldTest.kt:10)
HelloWorldTest > helloAnotherSampleName SKIPPED
4 tests completed, 1 failed, 2 skipped
```
Wait... didn't we just fix the test? Why is it failing? Take a closer look...
In fact, `helloSampleName()` *is* passing. It's just that at the same time,
we just inadvertently broke that first test: `helloNoName()`.
This is one tiny example of the benefit of maintaining a test suite: if we
use them to drive out our code, the second we break the program the tests
say so. Since we saw them passing just *before* our latest change,
whatever we *just* did most likely cause that regression.
Our latest change was making the greeting dependent on the name given. If
no name is given, our function defaults to an empty string. The intent is
that when `hello()` is called on no one in particular, our function greets
the whole world. Sound like a job for a default value!
`src/main/kotlin/HelloWorld.kt`:
```kotlin
fun hello(name: String = "World"): String {
return "Hello, $name!"
}
```
... and re-run the tests ...
```
$ gradle test
:compileKotlin
:compileJava UP-TO-DATE
:copyMainKotlinClasses
:processResources UP-TO-DATE
:classes UP-TO-DATE
:compileTestKotlin
:compileTestJava UP-TO-DATE
:copyTestKotlinClasses
:processTestResources UP-TO-DATE
:testClasses UP-TO-DATE
:test
HelloWorldTest > helloSampleName PASSED
HelloWorldTest > helloBlankName SKIPPED
HelloWorldTest > helloNoName PASSED
HelloWorldTest > helloAnotherSampleName SKIPPED
BUILD SUCCESSFUL
```
Excellent! Not only are both our tests passing, but that pesky warning
about not using `name` has faded into the distant past. We're now
(at least) three-fourth the way done. Just two more tests to go...
## Enabling and fixing the third test
(Re)open `src/test/kotlin/HelloWorldTest.kt` and find the penultimate test:
```kotlin
@Test
@Ignore
fun helloBlankName() {
assertEquals("Hello, World!", hello(" "))
}
```
In this test, we're trying to be tricky. It's one thing to omit a
parameter completely; it's a whole other situation when we provide a blank
string for a name. This test is telling us that we'd like to treat these
cases the same way.
... and remove it's `@Ignore` to enable it ...
```kotlin
@Test
fun helloBlankName() {
assertEquals("Hello, World!", hello(" "))
}
```
... and re-run the tests ...
```
$ gradle test
:test
HelloWorldTest > helloSampleName PASSED
HelloWorldTest > helloBlankName FAILED
org.junit.ComparisonFailure: expected:<Hello, [World]!> but was:<Hello, [ ]!>
at org.junit.Assert.assertEquals(Assert.java:115)
at org.junit.Assert.assertEquals(Assert.java:144)
at HelloWorldTest.helloBlankName(HelloWorldTest.kt:20)
HelloWorldTest > helloNoName PASSED
HelloWorldTest > helloAnotherSampleName SKIPPED
4 tests completed, 1 failed, 1 skipped
```
Since `" "` is an actual value, Kotlin does _not_ substitute in the
default value.
(Re)open `src/main/kotlin/HelloWorld.kt`.
```kotlin
fun hello(name: String = "World"): String {
return "Hello, $name!"
}
```
One way to handle this case is to check to see if `name` is blank. Let's
do that:
```kotlin
fun hello(name: String = "World"): String {
return "Hello, ${if (name.isBlank()) "World" else name}!"
}
```
As you can see, string templates can contain not just references to
variables, but entire expressions! This is appropriate in a case like this
where we want to apply a simple condition to a value.
... and rerun the tests ...
```
$ gradle test
:test
HelloWorldTest > helloSampleName PASSED
HelloWorldTest > helloBlankName PASSED
HelloWorldTest > helloNoName PASSED
HelloWorldTest > helloAnotherSampleName SKIPPED
BUILD SUCCESSFUL
```
We're almost there (perhaps closer than you think)! Just _one_ more test
to pass before we have a solution we can have real confidence in.
## Enabling the last test
(Re)open `src/test/kotlin/HelloWorldTest.kt` and find the last test:
```kotlin
@Test
@Ignore
fun helloAnotherSampleName() {
assertEquals("Hello, Bob!", hello("Bob"))
}
```
... and pop-off that `@Ignore` ...
```kotlin
@Test
fun helloAnotherSampleName() {
assertEquals("Hello, Bob!", hello("Bob"))
}
```
... then rerun the tests ...
```
:test
HelloWorldTest > helloSampleName PASSED
HelloWorldTest > helloBlankName PASSED
HelloWorldTest > helloNoName PASSED
HelloWorldTest > helloAnotherSampleName PASSED
BUILD SUCCESSFUL
```
Oh, hello! Turns out, the solution we put into place didn't just apply for
"`Alice`" but for "`Bob`" equally well. In this case, the test succeeded
with no additional code on our part.
Congratulations!
## Refactoring
Now that you've got all the tests passing, you might consider whether
the code is in the most readable/maintainable/efficient shape. What makes
for "good" design of software is a big topic. The pursuit of it underlies
much of what makes up the more valuable conversations on Exercism.
Kotlin is such a concise language and this exercise is so small, there is
not much room for us to make adjustments. Most would leave this code, as
is.
That said, we've taken such pains to illustrate two core parts of the
Test-Driven Development approach (i.e. "red", "green"), we'd be remiss if
we skipped the all important final part: "refactor".
More on TDD at http://www.jamesshore.com/Blog/Red-Green-Refactor.html.
The core responsibility of `hello()` is to produce a personalized greeting.
_How_ we determine whether or not a name is given (i.e. `name` is
effectively an empty string) is a lower-level detail.
```kotlin
fun hello(name: String = "World"): String {
return "Hello, ${if (name.isBlank()) "World" else name}!"
}
```
How would things read if we extracted that detail into a separate method?
```kotlin
fun hello(name: String = ""): String {
return "Hello, ${whom(name)}!"
}
private fun whom(name: String):String {
return if(name.isBlank()) "World" else name
}
```
By extracting that logic into the `whom()` method, we've added a little
abstraction to our program — it's not as literal as it was before. Yet,
it allows us to defer _needing_ to understand _how_ the recipient of the
greeting is determined.
If we can assume that `whom()` just works, we don't have to
downshift in our head to those details. Instead, we can remain at the same
level of thinking: what's the greeting?
_(Yes, this is considerable more lines of code; again, not a move we'd likely
make typically. The takeaway is this: when you are "done" with an exercise
ask yourself, "can I adjust the shape of this code to better tell the
story of what's going on through its shape?")_
We made a bunch of changes, let's make sure we didn't break the program!
```
$ gradle test
:compileKotlin
:compileJava UP-TO-DATE
:copyMainKotlinClasses
:processResources UP-TO-DATE
:classes UP-TO-DATE
:compileTestKotlin
:compileTestJava UP-TO-DATE
:copyTestKotlinClasses UP-TO-DATE
:processTestResources UP-TO-DATE
:testClasses UP-TO-DATE
:test
HelloWorldTest > helloSampleName PASSED
HelloWorldTest > helloBlankName PASSED
HelloWorldTest > helloNoName PASSED
HelloWorldTest > helloAnotherSampleName PASSED
BUILD SUCCESSFUL
```
This illustrates another benefit of writing tests: you can make significant
changes to the structure of the program and very quickly restore your
confidence that the program still works. These tests are a far cry from a
"proof" of correctness, but well-written tests do a much better job of
(very quickly) giving us evidence that it is. Without them, we manually
run the program with different inputs and/or inspecting the code
line-by-line — time-consuming and error prone.
# Submitting your first iteration
With a working solution that we've reviewed, we're ready to submit it to
@ -662,7 +260,7 @@ use the capitalized form on the person's name, regardless of the case they
used.
In that situation, you'd:
1. add a new test setting up that new expectation,
2. implement that in the code (the same process we just went through
together, above).

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@ -1,5 +1,5 @@
buildscript {
ext.kotlin_version = '1.0.2'
ext.kotlin_version = '1.2.40'
repositories {
mavenCentral()
}
@ -20,3 +20,9 @@ dependencies {
testCompile 'junit:junit:4.12'
testCompile "org.jetbrains.kotlin:kotlin-test-junit:$kotlin_version"
}
test {
testLogging {
exceptionFormat = 'full'
events = ["passed", "failed", "skipped"]
}
}

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@ -0,0 +1 @@
11001

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@ -0,0 +1 @@
8011001

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@ -0,0 +1 @@
4011001

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