►
Description
Build, debug, and test an application
Rust empowers developers to build reliable and efficient software. It is fun to write, easy to read, and high performing. Join Microsoft Program Manager Meaghan Lewis to explore some fundamental concepts and syntax of Rust through a simple command-line application. Along the way, she will debug, test, and clearly explain all the parts of the application.
About Meaghan Lewis
Meaghan Lewis currently focuses on creating and delivering learning experiences centered around emerging technology for Microsoft Reactors worldwide. Meaghan has a superpower in quality engineering and previously worked in the QA field for nearly a decade. Meaghan has a passion for teaching lifelong learners and has spent years speaking at conferences and delivering online courses. Meaghan is a native of California and lives in the San Francisco Bay Area with her husband and two dogs.
Rust Linz at https://rust-linz.at
Twitter: https://twitter.com/rustlinz
Meaghan Lewis: https://twitter.com/iammeaghanlewis
Speak at Rust Linz: https://sessionize.com/rust-linz
A
A
Then
I'm
going
to
transition
over
to
visual
studio
code,
where
I
will
build
debug
and
write
test
for
a
command
line,
interface
app
and
then
we'll
have
some
q
a
at
the
end,
but
also
feel
free
to
ask
questions
throughout.
If
there's
anything,
that's
not
clear
anything
that
pops
in
and
into
your
head
just
feel
free
to
pop
it
in
the
chat-
and
I
will
do
my
best
to
to
take
a
look
at
the
chat
and
answer
those
questions.
A
So
the
goal
really
is
just
to
get
more
comfortable
with
us
development
and
learn
about
helpful
tools
and
strategies
to
write
and
test
rest
apps
I'll
start
with
a
little
bit
of
an
overview
about
myself.
So
I'm
a
technical
program
manager
at
microsoft.
I've
been
in
this
role
going
on
about
a
year.
Now
it's
a
very
fun
role,
because
I
have
the
opportunity
to
be
a
content
creator.
A
I
focus
on
emerging
technologies
which
in
itself
is
very
broad,
so
I
have
a
lot
of
flexibility
and
freedom
to
decide
what
type
of
topics
and
content
that
I
want
to
create
and
rest
has
been
one
of
those
topics
that
I've
been
exploring.
I've
been
learning
for
the
past
year
so
about
the
time
that
I
joined
microsoft
and
I'll
talk
a
little
bit
more
about
my
journey
with
rust
and
what
I
enjoy
about
the
language,
but
yeah,
that's
a
little
bit
about
me.
A
So,
typically,
I
create
content
in
the
forms
of
talks
and
presentations
like
this.
I
do
some
twitch
streaming.
I
create
pre-recorded
videos,
write
blogs,
do
other
kind
of
stuff
so
really
like
all
over
the
place
with
content
creation,
I'm
also
part
of
the
microsoft
reactors
team.
So
this
is
typically,
you
know
who
I
am
creating
content
for.
So
microsoft
reactors
are
worldwide
communities
of
technologists
and
you'll
see
there
in
the
image
that
we
have
different
locations
around
the
world.
A
But
of
course,
since
march
of
this
year,
we've
fully
transitioned
to
online
delivery,
so
we've
been
able
to
offer
regular
workshops
and
live
streams,
typically
five
to
ten
per
week
across
a
variety
of
topics.
I
encourage
you
if
you
are
interested
in
learning
more
to
go
ahead
and
check
out
developer.microsoft.com
reactor,
and
we
also
have
a
whole
bunch
of
past
talks
on
youtube.com
microsoft
reactor
just
recently
in
the
past
week,
or
so.
A
A
You
know
projects
that
are
using
it
specifically
at
microsoft
and
such
we
also
had
a
couple
talks
from
ryan
levick,
who
was
at
the
speaker
at
the
last
meet
up
here
where
he
was
doing
a
couple
talks
on
on
kind
of
beyond
hello
world
getting
started
with
rust
as
well
as
kind
of
a
deep
dive
into
the
borrow
checker.
So
definitely
encourage
you
to
check
that
out
if
you're
interested
and
next.
So
what
I
like
about
rest,
I
mentioned
I've
been
learning
rust
for
the
past.
A
I
guess
year
or
so,
and
what
I
like
about
rust
is
that
you
know
there's
a
range
of
applications
that
you
can
build
with
it.
It's
you
know
for
web
and
system
systems,
programmers
you
can
build
command
line,
apps
web
assembly
embedded
apps
networking
so
like
the
list
goes
on
and
on
and
on
and
after
I
switch
out
of
this
presentation.
I'll
all
show
creates.I
o,
where
you
can
kind
of
learn
and
see
a
lot
more
applications
that
have
already
been
built
that
you
can
go
and
learn
from
and
use
yourself.
A
It
has
a
growing
community
and
a
passionate
community
of
developers
around
the
world,
and
I
think
this
is
really
exciting.
That's
always
you
know
it's
always
very
welcoming
to
join
your
project
where
there
are
friendly
developers,
people
who
just
want
to
learn
and
contribute,
and
it's
also
been
one
of
the
fastest
growing
languages
and
rated.
You
know
top
on
on
developer
surveys
like
stack
overflow
and
the
github
survey,
for
example.
So
that's
kind
of
you
know
what
interested
me
and
wanting
to
start
to
explore
rust.
It's
also
memory
stage.
A
Rust
is
a
really
good
job
of
making
it
difficult
to
leak,
memory
and
kind
of
along
the
same
lines
of
that
is
the
compiler.
So
I
think
the
compiler
and
rust
is
definitely
your
friend
and
it
is
super
helpful
to
figure
out
where
problems
are
happening
in
your
app
and
get
detailed
error
messages
about
problems
that
are
happening
in
your
app.
So
definitely
I
think
that
is
something
that
I
really
appreciate
and
we'll
spend
time
looking
looking
at
that
today.
A
So
the
tools
that
I'm
going
to
be
using,
I
mentioned
visual
studio
code.
I
pretty
much
use
visual
studio
code
for
anything,
especially
anything
coding
related,
but
sometimes
even
beyond
that
so
highly
recommend
that
ide,
I'm
also
going
to
be
using
the
rest,
analyzer
extension
and
I'm
also
going
to
be
using
lldb,
which
is
a
debugger
for
vs
code
and
rust.
Analyzer
is
going
to
help
provide
us
with
a
little
bit
of
language
support
and
also
demonstrate
how
that
works
momentarily.
A
So
now,
I'm
going
to
transition
over
to
the
demonstration
and
what
I'm
going
to
do
is
build
a
command
line.
Interface
app
to
just
generate
a
password
of
a
provided
link.
So
then,
after
I
write
the
app
I'm
gonna
do
some
debugging
and
write
test,
as
I
mentioned,
and
I
just
decided
to
start
with
a
command
line
app.
I
think
this
is
a
great
way
to
start
to
get.
A
You
know
familiar
with
the
the
language
itself,
so
get
familiar
with
the
syntax
and
different
things,
and
I
think
this
is
all
just
a
great
way
to
learn
any
language
in
general,
so
that's
kind
of
where
I've
been
dabbling
and
creating
various
command
line.
Apps.
It's
also
nice
because
you
can
pretty
much
get
immediate
feedback.
You
can
write
something
go
to
compile
and
run
it
and
kind
of
see
instantly
like
how
things
are
working.
So
that's
one
deciding
to
go
in
this
direction.
A
A
A
All
right,
oops,
sorry,
one
second,
I
actually
needed
to
cd
to
that
directory
and
now,
let's
open
this
up
in
code
and
not
my
whole
projects
directory
okay,
and
while
I
do
that,
I
also
do
want
to
make
sure
that
I
can
see
the
chat
and
the
background.
And
of
course
I
do
encourage
you
to
ask
questions
so
I'll.
Try
to
keep
that
up
all
right.
A
So
what
I
am
given
here
is
in
my
source
directory.
I
have
this
being
done,
rs
program,
I
also
have
a
cargo.lock
and
that
cargo.tunnel
file
for
package
information
as
well
as
that's
where
I
can
store
dependencies
for
my
project,
so
I
am
going
to
start
in
the
main.rs,
but
before
I
do
that,
I
do
want
to
remember
to
actually
show
the
extensions
that
I
was
talking
about
before.
A
So
I
mentioned
rest
analyzer
and
you
can
just
search
over
in
the
extensions
bar
if
you
want
to
get
there
and
download
this
extension,
we'll
see
how
this
works,
I'm
just
kind
of
showing
you
how
to
get
there.
I'm
also
going
to
be
using
the
code,
lldb
extension
for
debugging,
so
you
can
just
type
in
lldb
there's
a
variety
of
different
ones.
There
or
type
in
code
ll
db
directly
to
go
ahead
and
get
there.
A
So
now,
let's
hop
back
over
to
the
code
and
I'm
going
to
start
filling
in
the
contents
of
my
program
so
that
I
can
generate
this
password
with
a
given
length.
So
what
I
want
to
do
right
off
the
bat
is
be
able
to
generate
and
rather
collect
command
line
arguments,
and
so
what
I'm
going
to
do
is
use
a
crate
called
struck
up.
So
let
me
go
ahead
and
show
that
and
I'll
hop
back
over
a
little
bit
just
to
kind
of
show.
I
mean
crates,
I'm
using
documentation,
helpful
things.
A
This
is
also
how
I
would
just
be
developing
on
my
own,
so
there's
sometimes
some
context.
Switching,
so
the
crate
that
I
want
to
use
is
called
struct,
opt
and
so
struct
opt.
If
I
look
at
it,
it's
gonna
allow
me
to
parse
command
line
arguments
by
defining
a
struct,
and
what
this
does
is
combine,
clap
which
stands
for
command
line.
A
Argument,
parser
for
rest
with
a
custom
derived,
so
it's
basically
just
going
to
allow
me
to
use
a
struct
to
collect
command
line
arguments
and
creates
that
io
is
very,
very
awesome.
Usually
you
can
get
a
lot
of
information
about.
You
know
how
to
include
this
crate
in
your
dependency
file,
the
cargo
tunnel,
as
well
as
just
examples
about
how
to
use
this.
So
let
me
go
ahead
and
copy
this
over,
so
that
I
can
use
it
in
nvs
code
and
then
we'll
hop
back
over
there.
A
A
A
A
So
I
want
to
specify
a
a
short
option
which
will
be
used
if
I
type
l
to
use
that
option,
I'm
going
to
specify
a
long
option
of
length,
so
I
can
use
dash
length
to
use
this
option
and
I'm
also
going
to
specify
a
default
value
which
is
going
to
be.
Let's
just
say
12:
this
can
be
any
default
value
of
your
choice
and
following
that
I
actually
want
to
specify
the
parameter
that
I
want
to
collect.
So
this
is
going
to
be
a
length
of
type
view
size.
A
A
Called
ops
is
equal
to
ops
from
underscore
arcs,
and
you
see
the
rest
analyzer
helping
me
out
a
little
bit
more
there
so
from
rx
is
going
to
allow
me
to
get
the
command
line,
arguments
from
the
struct
and
immediately
following
this.
Let's
just
do
a
print
lens,
I'm
gonna
use
that
print
ln
macro
and
I
want
to
be
able
to
print
out
the
struct,
and
I
can
print
it
out
like
this
and
then
let's
just
go
ahead
and
get
ops
all
right
and
right
off
the
bat.
A
I
just
want
to
kind
of
run
what
I've
done.
So
I'm
going
to
open
up
my
terminal
down
here
and
what
I
want
to
say
is
cargo
run,
so
I'm
just
going
to
run
it
you'll
notice
that
it's
going
to
compile
the
different
crates
and
the
dependencies
that
I'm
using
and
after
that
I'll
see
that
it
is
running
and
that
I
get
my
ops
printed
out
there
at
the
bottom.
So
we
just
have
that
default
of
12..
I
can
also
then
test
out
how
I
can
input
the
options.
A
So
what
changes
there
is
that
I
now
get
a
new
length
of
30,
so
that
is
not
using
the
default
it's
using.
What
is
defined
through
the
command
line,
all
right,
I'm
going
to
keep
going
check
in
if
there
are
any
questions
yet
so
next,
what
I
want
to
do
is
start
to
actually
kind
of
build
out
the
function
and
the
rest
of
the
functionality
to
generate
the
password.
So
I'm
going
to
say
let
length
so
I'm
just
going
to
define
a
new
variable
called
length
is
equal
to
ops,
dot.
A
Length
and
then,
following
that,
I'm
going
to
also
define
a
new
variable
called
password
and
in
this
what
I
eventually
want
to
do
is
be
able
to
call
this
function
generate
password,
which
I
do
not
have
yet.
So
I
will
get
the
compiler
yelling
at
me,
which
I'll
fix
momentarily
and
then,
after
that,
what
else
I
would
want
to
do
is
go
ahead
and
print
out
the
password.
So
I
can
just
say:
password
is,
and
just
have
this
placeholder
here
for
me
to
eventually
fill
out
the
password.
A
There
we
go
all
right
so
now,
right
below
the
main
function.
What
I'm
going
to
start
to
do
is
actually
define
this
generate
password
function.
So
let's
go
ahead
and
say:
fn
generate
password,
it
already
kind
of
knows
what
I'm
doing
here.
So
that
is
going
to
take
a
parameter
of
both
lengths.
There
we
go,
which
is
type
view
size,
and
then
it's
inevitably
going
to
return
a
string
that
we
get
back
here
when
we
call
the
function.
A
Okay,
so
that's
going
to
return
a
string
like
that
and
then
let
me
go
ahead
and
start
to
fill
in
the
contents
of
this
generate
password
function
before
I
do
that,
I
just
want
to
call
out.
I
am
going
to
be
using
the
rand,
liver
or
great
rather
to
go
ahead
and
generate
random
numbers
and
just
kind
of
giving
overview,
I'm
going
to
be
generating
random
numbers,
or
rather
kind
of
selecting
numbers
from
a
character
set
that
I
can
provide
of
all
the
possible
values
that
we
can
use
in
our
password.
A
And
just
like
before,
I
can
see
all
kinds
of
information
here,
there's
links
to
the
documentation
which
we'll
probably
check
out
just
momentarily,
because
I
think,
if
I
recall,
there's
not
so
many
examples
here
and
I
like
to
see
the
examples,
but
I
do
see
how
to
use
this
and
my
cargo
tunnel
so
I'll
copy
that
for
now
and
just
go
in
and
check
out
the
documentation.
I
also
just
want
to
call
out
that
I
think
the
documentation
and
rest
is
usually
fantastic.
A
You
can
get
lots
of
helpful
information
here.
You
can
see
different
examples
about
actually
how
to
use
this
crate
and
and
different
different
models
and
things
that
it
provides
so
yeah.
I'm
gonna
do
something
kind
of
similar
to
what
you
see
here,
but
let's
hop
back
over
to
vs
code.
So
I
can
show
that,
and
so,
if
I
go
back
over
to
cargo.tommol
online
11,
I'm
going
to
go
ahead
and
paste
this
rand
crate
and
you
might
even
notice
down
at
the
very
bottom
of
vs
code
and
it
stopped
doing
it
now.
A
But
you'll
notice
that,
even
as
I'm
writing
code,
the
rust
analyzer
is
kind
of
doing
things,
it's
kind
of
always
checking
so
what
it
just
did
basically
was
kind
of
compile
this
rand
crate
for
me.
So
it's
already
aware
without
me,
even
having
to
kind
of
go
back
to
the
terminal
and
use
cargo
compile,
for
example.
A
A
And
after
that,
I
am
getting
a
little
distracted
by
the
error
message,
but
we
will
figure
it
out.
What
I
want
to
do
next
is
actually
define
the
possible
characters
that
I
can
use
to
pick
from
randomly
and
generate
this
password.
So
I'm
going
to
define
a
new
constant
using
that
const
keyword
and
this
is
going
to
be
called
car
set
and
car
set.
Is
it's
going
to
basically
define
all
of
the
uppercase
letters,
lowercase
letters,
digits
and
symbols
that
I'm
going
to
be
using?
A
A
A
So
a
map
is
going
to
basically
produce
a
new
iterator
which
is
going
to
allow
me
to
pass
in
those
values
that
I
defined
above
so
starting
at
zero
up
until
11
or
whatever
the
length
of
the
password
is
that
I
define,
but
it
is
12
by
default,
and
then
I
can
use
this
annotation
to
basically
just
say:
I'm
going
to
start
to
pass
in
again
each
one
of
those
iterators
and
it's
going
to
get
a
little
bit
messy
but
we'll
get
there.
So
that's
gonna!
A
I
want
to
define
a
new
variable
called
idx,
and
this
index
is
going
to
call
this
gen
range
function
and
jin
range
is
going
to
be
expecting
a
range
from
low
to
high.
So
it
knows
that
it
wants
to
generate
this
random
number.
It
just
is
looking
for
a
little
bit
of
direction
about
what
to
generate
within
the
range
to
generate
within.
A
All
right
and
then
what
I
want
to
do
next
is
just
for
each
of
the
indexes.
I
want
to
then
mount
that
to
a
character,
and
let
me
just
finish
this,
so
we
can
get
all
that
red
out
of
here
and
it
could
look
a
little
bit
nicer
and
then
I
will
go
back
so
what
this
is
going
to
do,
and
I'm
going
to
shortly
deflect
this.
So
we
can
see
exactly
what's
happening
in
here
is
for
each
index
so
starting
at
zero
up
until
the
the
length
of
this
character.
A
This
car
set
I'm
going
to
pass
in
a
different
index,
so
eventually
we're
going
to
get
as
many
indexes
as
the
link
as
different
characters
and
then
we're
going
to
collect
that.
So
we
want
to
call
this
collect
method,
and
if
I
hover
over
this-
and
you
can
hover
over
pretty
much
anything,
the
rust
analyzer
will
tell
me
lots
of
information
about
what
this
is,
how
you
know
how
to
use
something
provide
me
with
some
tips.
So
I
see
that
this
will
transform
an
iterator
into
a
collection.
A
So
collect
is
a
common
method
that
is
used
with
an
iterator,
and
this
is
just
going
to
return
me
a
collection
and,
if
I'm
looking
through
here,
what
jumps
out
to
me
is
a
string
is
going
to
be
a
collection
of
cars.
So
I
am
collecting
all
of
these
cars
one
by
one
up
until
the
full
length
of
the
password
that
I
want
and
then
I'm
going
to
return
that
as
a
string
collection,
and
so
then
that
satisfies
this
return
type
up
here
and
let's
go
ahead
and
try
this
out.
A
Everything
is
looking
pretty
happy
for
now.
So
let's
go
ahead
and
try
this
out
yeah,
I
was
getting
some
output
earlier
about
errors,
so
the
rest
analyzer
again
is
kind
of
always
helping
me
out
there.
Sometimes
I
just
ignore
them
until
I'm,
you
know
ready
and,
as
I'm
kind
of
you
know,
still
writing
I'll
ignore
them
until
I
come
back
and
have
time
to
look
at
what
I
did
wrong.
So
let's
go
ahead
and
just
try
a
cargo
red
again.
A
It's
doing
some
more
compiling.
I
get
the
ops
printed
out
as
well
as
excuse
me
as
well
as
the
password
that
is
generated
here.
So
let's
now
go
back
up
and
I
actually
want
to
go
ahead
and
debug
this
and
we're
going
to
debug
I'm
going
to
set
a
breakpoint
here,
so
we
can
start
to
see
specifically
what's
happening
and
what
this
idx
variable
is
kind
of
getting
as
we
run
through
this
iterator.
A
A
A
A
A
A
A
If
I
step
over,
I
see
that
our
index
is
63,
so
this
index
is
basically
gonna,
be
returning
me
an
ascii
value,
so
it's
going
to
be
able
to
kind
of
get
the
character
in
the
character
set
based
on
that
value,
and
let's
see
if
I
were
to
go
over
this
again-
oh,
I
didn't
want
to
go
that
way
now.
So,
okay,
I
just
continued
playing,
so
it
ran
through
that
iterator
once
and
it
stopped
at
the
breakpoint
again
and
notice.
A
A
But
it's
going
to
kind
of
allow
me
to
really
see
what's
happening
at
different
parts
of
the
program
and
then
kind
of
make
sure
that
I'm
on
the
right
track
and
confirm
that
I'm
kind
of
getting
the
right
values
that
I
expect
so
I
definitely
recommend
using
a
debugger
and
if
you've
used,
you
know
debuggers
for
any
other
programming
language.
This
is
probably
very
familiar
with
you.
A
You
can
pretty
much
debug
anything
that
you
that
you
feel
like
debugging,
but
typically
I'm
using
it
somewhere,
where
I
want
to
learn
a
little
bit
more
information,
and
I
just
again
when
I
like
know
that
something
is
working.
The
way
that
I
expect
it
to
so.
This
will
continue
to
cycle
through.
I'm
gonna
just
go
ahead
and
stop
this.
A
For
now
I
see
that
the
process
exited-
I
don't
see
any
other
information
there,
because
I
guess
I
just
stopped
it,
but
if
I
wanted
it
to
run
all
the
way
through,
I
could
do
that
and
eventually
see
the
output
where
I
would
ultimately
return
this
collection
of
a
string
and
then
get
it
will
be
able
to
print
the
password
out.
So
that's
kind
of
a
little
bit
of
an
overview
about
debugging,
we'll
come
back
to
that
momentarily.
A
A
All
right
and
before
I
do
that
there
is
actually
something
else
that
I
want
to
do
very
quickly,
but
as
I'm
thinking
about
you
know
for
now
this
this
this
program
is
very
short
and
sweet,
but
I
might
want
to
start
to
you
know,
add
more
functionality.
I
might
want
to
collect
other
command
line
arguments.
Perhaps
I
want
to
specify
what,
in
the
character
set
that
I
want
to
use?
A
If
I
want
to
use,
you
know
uppercase
if
I
want
to
include
symbols,
so
I
can
start
to
kind
of
collect
a
lot
more
information
and
just
make
my
program
more
advanced.
This
is
a
very
simple
implementation
that
we
just
did,
but
I
also
want
to
think
about
how
to
kind
of
isolate
and
and
really
have
my
main
program
focus
on
on
just
the
program
execution
where
I
can
have.
A
Maybe
some
of
the
the
supporting
functionality
be
moved
to
a
library,
so
I
do
want
to
show
that
and
then,
when
I
move
all
this
to
a
library
we'll
go
ahead
and
test
over
there,
I'm
going
to
look
at
this
breakpoint
for
now,
and
so
what
I'm
going
to
do
inside
of
my
source
directory
is
create
a
new
source
file
called
lib.rs,
and
I'm
going
to
go
ahead
and
paste.
This
function
definition
over
here,
I'm
also
going
to
need
to.
A
Use
the
random
the
rand
crate
over
here,
so
I
can
go
ahead
and
paste
that
and
then
of
course,
now
that
I
have
moved
this
function
over
to
the
library
the
compiler
is
having
a
hard
time
finding
this.
This
generate
password
function.
So
what
I
can
do
is
first
just
use
the
package
name
to
call
that
so
the
package
name
is
gpw
the
same
name
as
my
project.
A
If
I
go
back
over
to
my
library
program,
what
I
need
to
do
is
make
this
a
public
function,
because
the
compiler
will
complain
that,
even
though
you
know
this
library
program
and
my
main
program
are
part
of
the
same
package,
just
the
way
that
rest
visibility
is
set
up,
we
need
to
explicitly
make
sure
that
we
can
access
other
library
functions,
so
that
should
be
fine.
Now,
let's
just
try
this
out
to
make
sure
that
everything
runs
as
expected.
A
A
A
We
only
have
one
function,
so
this
should
be
pretty
seamless
and
you
want
to
kind
of
test
to
make
sure
that
you're
getting
the
right
output.
You
want
to
test
the
happy
path
scenarios,
which
is
just
going
to
be
the
quickest
case
like
confirming
that
this
function
executes
as
expected.
We
also
want
to
start
to
think
about
what
could
go
wrong
and
test
for
that.
So,
typically,
you
want
to
put
unit
tests
in
each
file
that
they're
testing.
So
this
is
my
library
file.
A
A
A
And
then
we
can
use
an
assertion,
so
let
me
step
back
just
a
moment
and
you'll
notice
that,
as
I
started
typing
assert
that
I
got
suggestions
like
I've
done
previously.
I
wanted
to
call
out
specifically
that
russ
provides
a
couple
assertions
that
I
can
use
as
macros
right
off
the
bat.
So
this
is
very
nice
as
opposed
to
possibly
having
to
integrate
with
some
other
kind
of
assertion.
Library
or
framework,
like
you
have
to
do
another
programming
language.
A
You
can
kind
of
get
these
simple
assertions,
so
I
have
a
search,
equal
or
not.
Equal,
there's
also
a
regular
just
assert.
So
you
can
kind
of
put
more
custom
assertions
within
that
in
that
macro.
But
let's
go
ahead
and
just
use
the
search
equal
for
now
and
what
I
can
do
is
go
ahead
and
say
password
dot.
B
A
A
Might
be
a
little
too
big,
okay,
so
you'll
notice
here.
This
is
our
first
time
running
test
right
off
the
bat
we're
able
to
run
one
test,
which
is
this
test
that
I
just
defined
here
then
there's
also
a
couple
other
places
where
cargo
is
looking
for
tests.
So
here
it's
looking
for
tests
in
my
main
program
and
then
I'm
also
looking
for
doc
test
so
doctest,
hopefully
we'll
have
a
little
bit
of
time.
A
To
get
to
that,
I
think
a
really
cool
feature
of
rust
is
that
it
does
encourage
documentation
testing.
So
within
you
know
any
library
or
other
program.
I
should
think
about
including
very
detailed
documentation,
which
is
going
to
include
examples
and
also
tests
of
how
to
use
particular
functions
and
and
other
features.
So
that's
a
very,
very
cool.
A
I
think
it
also
encourages
folks
to
kind
of
keep
their
documentation
up
to
date,
since
it
is
kind
of
a
living
part
of
your
program
and
when
you
actually
compile
the
program
you'll
you'll
know
like
we
see
here
whether
or
not
those
tests
are
are
correct,
so
it
does
encourage
folks
to
keep
their
their
documentation
up.
To
date,
all
right,
so
we
were
able
to
run
that
test.
A
Vs
code
does
provide
nice
options
about
like
reformatting.
I
can't
find
that,
as
of
now,
there's
probably
a
shortcut,
I'm
missing,
but
we
are
able
to
now
have
our
test
inside
of
a
module,
and
let
me
just
go
ahead
and
run
this,
and
I
can
also
click
on
this
run
test
option
to
run
the
test
from
here.
What
happens
now
is
I
do
get
a
error
because
generate
password
is
not
found
in
the
scope.
A
Now
that
I
have
a
module
within
this
library
program,
I
still
just
can't
access
this
function,
even
though
it
is
public,
so
something
that
you'll
see
generally
used
within
a
test
module.
Is
this
keyword
years
super
which
is
just
essentially
going
to
allow
me
to
access
and
kind
of
inherit
and
use
the
functionality?
That's
part
of
this
library.
A
All
right,
let's
just
try
that
again:
okay,
press
any
key
to
close
and
let's
go
ahead
and
try
cargo
test
again
cool,
and
then
that
should
have
satisfied
it.
Sometimes.
I
still
get
errors,
but
I
think
we're
all
good
to
go
here.
So
that
is
something
to
keep
in
mind
if
you
are
using
vs
code,
it's
always
helpful
to
use
kind
of
a
combination
of
you
know:
rust,
analyzer,
helping
you
out,
as
well
as
the
terminal
and
using
cargo
directly
to
run
your
testing
programs.
A
A
So
in
rest,
integration
tests
are
external
to
your
library,
so
they
kind
of
use
your
library
in
the
same
way,
but
you
should
think
of
integration
tests
as
first
you
know
you
want
to
test
that
parts
of
your
program
can
work
properly
together
when
integrated,
and
you
also
just
want
to
test
kind
of
assuming
that
you
are
your
user.
So,
however,
your
user
would
interact
with
your
program,
so
that's
kind
of
form,
more
of
a
higher
level
where
you're
not
thinking
about
testing
each
particular
function
but
more
of
the
program
as
a
whole.
A
Okay,
there
we
go
it's
outside
of
source
now,
so
this
is
going
to
be
called
test
and
that's
just
the
general
convention
that
you
use
within
this
test
directory,
I'm
going
to
create
a
new
file
and
let's
just
go
ahead
and
call
this
new
file.
Gpw
underscore
test
dot,
rf,
all
right,
and
so
what
I
want
to
do
in
here
is
write
a
test.
That's
essentially
just
going
to
test
my
generate
password
program,
not
function
in
particular
but
more
of
the
program.
A
There
we
go.
Sometimes
this
takes
a
minute,
and
so
what
this
is
going
to
allow
me
to
do
is
simplify
the
process
of
testing
my
command
line
interfaces,
so
we
can
use
it
like
this.
So
here's
just
a
small
example:
trivial
example
where
we
can
define
a
cmd
variable
and
we
use
this
cargo
ben
function
to
basically
tell
cargo
to
to
run
whatever
command
that
we
enter
here
and
then
it
does.
This
unwrap
so
essentially,
unwrap
is
going
to
be
looking
for
whatever
the
response
is
after
we
call
this
function.
A
So
whatever
you
know,
if
it's
successful,
if
it's
a
failure,
whatever
other
kind
of
information
we
might
receive
back,
I
will
be
able
to
capture
there
and
then
we
can
do
something
like
assert
success
or
exert
failure
or
assert
other
specific
things.
I
just
see
the
trivial
example
here.
It
might
be
helpful
to
actually
look
in
the
documentation
to
see
some
more
detailed
examples
about
how
to
use
that.
A
And
it
looks
like
there's
some
more
detail
here,
so
here's
a
little
a
more
detailed
example
about
kind
of
how
you
can
have
a
more
complex
test,
testing,
different
things
and
asserting
different
information
cool.
I
will
possibly
come
back
to
that,
but
now
that
I
have
copied
the
version
of
that
crate
that
I
want
to
use.
I
can
just
go
ahead
and
paste
it
in
my
cargo.tamal
and
going
back
to
the
test
directory
or
the
test
program
at
the
top
of
my
file.
A
And
then
here
I
want
to
just
use
this
test
annotation,
something
that
I
should
call
out
is
with
integration
tests
that
are
already
in
their
own
test
directory.
You
don't
have
to
worry
about
using
kind
of
that
config
command
to
specify
that
this
is
a
test
and
kind
of
make
it
a
specific
module,
because
it
is
already
in
its
own
directory.
It's
pretty
much
only
going
to
be
run
and
compiled
when
you
call
cargo
test
anyway.
A
A
Something
else
we
should
try
to
do
is,
of
course,
write
different
tests.
I
don't
think
I'm
going
to
get
into
very
much
many
more
examples
for
now,
but
just
you
should
also
confirm
that
even
your
tests
are
working
as
expected.
So
it's
it's
helpful.
You
know
if
you
want
to
do
something
like
test
driven
development
and
maybe
write
a
failing
test
first
or
otherwise
just
want
to
know
that
your
test
can
fail.
I
recommend
doing
that.
A
So,
for
example,
I
just
changed
the
success
to
failure
and
I
can
see
that
that
does
in
fact
fail
my
program
because
it
was
able
to
run
it
successfully.
So
I
always
recommend
just
either.
You
know,
writing
various
tests
and
also
making
sure
that
your
tests
can
both
pass
and
fail
so
that
they
are
valid.
So
that
is
a
quick
example
of
an
integration
test.
A
And
then
I
think
for
now
time
permitting.
I
just
did
a
time
check,
I
think
I'm
at
about
45
or
maybe
a
little
bit
less
35
minutes.
So
let
me
switch
back
over
now
to
the
rest
of
my
slides.
Now,
I'm
going
to
show
information
where
I
kind
of
have
a
more
complete
demo
and
then
more
examples
of
tests
that
you
can
check
out.
So
where
is
that
don't.
A
A
This
code
is
more
complete.
It
has
a
little
bit
more
examples,
including
kind
of
a
more
defined
function
for
the
generate
password,
as
well
as
just
other
tests,
where
I
am
kind
of
doing
both
more
happy
path
and
side
path,
there's
also
an
example
of
a
documentation
test,
so
I
do
recommend
checking
that
out
as
well
as
I
just
mentioned,
crates.io,
and
that's
something
that
I
didn't
share
before,
but
in
crates.io
and
just
the
home
page,
you
could
get
a
bunch
of
information
right
off
the
bat.
B
Megan,
thank
you
very,
very
much.
Thank
you
for
this
great
presentation
and
kudos.
I
am
a
presenter
myself
and
I
know
that
you
have
to
be
very,
very
brave
to
do
so
much
life
coding,
so
really
awesome.
We
have
one
or
two
questions,
especially
here
on
on
discord.
People
were
chatting
a
lot
about
what
use
what
you
showed,
and
even
some
some
guy
said.
Hey.
I
didn't
know
this
crate
and
so
on
so
really
great
presentation.
B
A
Oh
okay,
so
I
mean
I
I
just
heard
great
things
about
this.
This
extension
in
particular,
I
think
you
know
I
recommend
trying
them
out
you'll
notice
that
I
do
have
this
this
extension
installed.
That's
kind
of
my
process
personally
is
like
trying
out
different
extensions.
I
think
you'll
often
find
that
there
might
be
very
similar
extensions
that
kind
of
provide
the
same
help
and
functionality.
A
B
Absolutely
thank
you
very
much.
Yeah
we'll
definitely
try
that
out
and
then
we
had
a
short
discussion.
I
think
it
was
in
your
lib.rs
on
github.
I
just
checked
it
out.
It
was
in
line
13..
I
can't
remember
what
it
was
here
a
little
bit
up.
I
think
yeah
here
is
line.
Seven
people
are
asking
why
you
are
specifically
using
a
reference
to
an
unsigned
eight
here
and
not
just
using
a
reference
to
a
string.
Is
there
a
specific
reason?
Is
it
necessary
for
your
code
or
any
comments
on
that.
A
Yeah,
so
the
question
is
why
I'm
okay,
let
me
try
to
repeat
the
question.
I
think
there
are
a
couple
different
things:
why
I'm
using
kind
of
the
unsigned
eight
character
or
constant,
rather
than
like
you
know,
just
making
this
a
regular
string
and
just
why
it
is
that
type
and
in
general,
so
I
wanted
to
just
make
this
a
constant
set
of
characters
and
really
why
I
ultimately
wanted
to
do
that.
Yeah,
I'm
going
to
start
there
and
then
come
back.
A
A
I
also
had
to
define
this
as
a
unsigned
8-bit
type,
because
that
is
basically
what
this
const
is
going
to
expect
with
the
value
that
I'm
providing,
which
is
this
fight
string
literal
in
this
way.
So
that's
at
least
why
I'm
using
the
type
yeah
I
could
have
chose
to
do
something
differently.
It
just
seemed
like
a
reasonable
choice
at
the
time
and
kind
of
being
able
to
again
like
iterate
over
each
one
of
these
characters,
and
then
this
collect
is
specifically
returning
a
collection
of
strings
based
on
characters.
B
Thank
you.
Thank
you
very
much
for
elaborating
about
that.
I
think
that
describes
how
you
why
you
went
for
that
and
also
in
the
discord
server.
Some
other
members
of
the
community
posted
some
links
to
the
documentation
for
those
of
you
who
were
asking
this
question
and
you
want
to
know
more
check
out
our
discord,
technical
discussion
channel
and
you
will
find
some
people
there
who
posted
interesting
links
on
that
topic
too.