fuzz: update README instructions (#1175)

Signed-off-by: Takeshi Yoneda <[email protected]>

internal/integration_test/fuzz/README.md

@@ -9,17 +9,26 @@ Fuzzing infrastructure for wazero engines via [wasm-tools](https://github.com/by
 
 ### Run Fuzzing
 
-Currently, we only have one kind of fuzzing named `basic` where we compare the results from the compiler
-and interpreter engines, and see if there's a diff in them. To run the test, execute the following command:
+Currently, we have the following fuzzing targets:
+
+- `basic`: compares the results from the compiler and interpreter engines, and see if there's a diff in them.
+- `memory_no_diff`: same as `basic` except that in addition to the results, it also compares the entire memory buffer between engines to ensure the consistency around memory access.
+  Therefore, this takes much longer than `basic`.
+- `validation`: try compiling maybe-invalid Wasm module binaries. This is to ensure that our validation phase works correctly as well as the engines do not panic during compilation.
+
+
+To run the fuzzer on a target, execute the following command:
 
 ```
 # Running on the host archictecture.
-cargo fuzz run basic
+cargo fuzz run <target>
 
 # Running on the specified architecture which is handy when developping on M1 Mac.
-cargo fuzz run basic-x86_64-apple-darwin
+cargo fuzz run <target>-x86_64-apple-darwin
 ```
 
+where you replace `<target>` with one of the targets described above.
+
 See `cargo fuzz run --help` for the options. Especially, the following flags are useful:
 
 - `-jobs=N`: `cargo fuzz run` by default only spawns one worker, so this flag helps do the parallel fuzzing.
@@ -29,6 +38,19 @@ See `cargo fuzz run --help` for the options. Especially, the following flags are
 - `-timeout` sets the timeout seconds _per fuzzing run_, not the entire job.
 
 
+#### Example commands
+
+```
+# Running the `basic` target with 15 concurrent jobs with total runnig time with 2hrs.
+$ cargo fuzz run basic -- -max_len=5000000 -max_total_time=7200 -jobs=15
+
+# Running the `memory_no_diff` target with 15 concurrent jobs with timeout 2hrs and setting timeout per fuzz case to 30s.
+$ cargo fuzz run memory_no_diff -- -timeout=30 -max_total_time=7200 -jobs=15
+
+# Running the `validation` target with 4 concurrent jobs with timeout 2hrs and setting timeout per fuzz case to 30s.
+# cargo fuzz run validation -- -timeout=30 -max_total_time=7200 -jobs=4
+```
+
 ### Reproduce errors
 
 If the fuzzer encounters error, you would get the output like the following: