diff --git a/test/run_tests.sh b/test/run_tests.sh
index e5993a79..427dcd1e 100755
--- a/test/run_tests.sh
+++ b/test/run_tests.sh
@@ -125,6 +125,62 @@ test_touch_and_rm_D_flag_commit()
         [ ! -f file.txt.gz ]
 }
 
+test_reuse_sandbox()
+{
+    local try_workspace=$1
+    cp $RESOURCE_DIR/file.txt.gz "$try_workspace/"
+    cd "$try_workspace/"
+    
+    ## Set up expected output
+    echo 'test' >expected2.txt 
+    echo 'test2' >>expected2.txt 
+    touch expected3.out
+
+    try_example_dir=$(mktemp -d)
+    "$try" -D $try_example_dir "touch file_1.txt; echo test > file_2.txt; rm file.txt.gz"
+    "$try" -D $try_example_dir "rm file_1.txt; echo test2 >> file_2.txt; touch file.txt.gz"
+    $try commit $try_example_dir
+    
+    [ ! -f file_1.txt ] &&
+        diff -q expected2.txt file_2.txt &&
+        diff -q expected3.out file.txt.gz
+}
+
+test_reuse_problematic_sandbox()
+{
+    local try_workspace=$1
+    cp $RESOURCE_DIR/file.txt.gz "$try_workspace/"
+    cd "$try_workspace/"
+    
+    ## Set up expected output
+    echo 'test' >expected2.txt 
+    echo 'test2' >>expected2.txt 
+    touch expected3.out
+
+    try_example_dir=$(mktemp -d)
+    "$try" -D $try_example_dir "touch file_1.txt; echo test > file_2.txt; rm file.txt.gz"
+
+    ## KK 2023-06-29 This test is meant to modify the sandbox directory in an illegal way,
+    ##               at the moment, this modification will be caught as illegal by `try`,
+    ##               but it doesn't seem to both overlayfs at all.
+    ## TODO: Extend this with more problematic overlayfs modifications.
+    touch "$try_example_dir/temproot/bin/foo"
+    ! "$try" -D $try_example_dir "rm file_1.txt; echo test2 >> file_2.txt; touch file.txt.gz"
+}
+
+test_non_existent_sandbox()
+{
+    local try_workspace=$1
+    cp $RESOURCE_DIR/file.txt.gz "$try_workspace/"
+    cd "$try_workspace/"
+    
+    try_example_dir="non-existent"
+    ! "$try" -D $try_example_dir "touch file_1.txt" 2>/dev/null &&
+    ! "$try" summary $try_example_dir 2>/dev/null &&
+    ! "$try" commit $try_example_dir 2>/dev/null &&
+    ! "$try" explore $try_example_dir 2>/dev/null 
+}
+
 test_pipeline()
 {
     local try_workspace=$1
@@ -266,6 +322,9 @@ if [ "$#" -eq 0 ]; then
     run_test test_untar_D_flag_commit
     run_test test_touch_and_rm_no_flag
     run_test test_touch_and_rm_D_flag_commit
+    run_test test_reuse_sandbox
+    run_test test_reuse_problematic_sandbox
+    run_test test_non_existent_sandbox
     run_test test_pipeline
     run_test test_cmd_sbst_and_var
     run_test test_summary
diff --git a/try b/try
index 7e425e95..7a64529a 100755
--- a/try
+++ b/try
@@ -22,7 +22,24 @@ TRY_VERSION="0.1.0"
 try() {
     START_DIR="$PWD"
 
-    [ "$SANDBOX_DIR" ] || SANDBOX_DIR=$(mktemp -d)
+    if [ "$SANDBOX_DIR" ]
+    then
+        ## If the name of a sandbox is given then we need to exit prematurely if its directory doesn't exist
+        [ ! -d "$SANDBOX_DIR" ] && { printf "%s: could not find directory $SANDBOX_DIR\n" "$(basename $0)" >&2; exit 2; } 
+    else
+        ## Create a new sandbox if one was not given
+        SANDBOX_DIR=$(mktemp -d)
+    fi
+
+    ## If the sandbox is not valid we exit early
+    if ! sandbox_valid_or_empty "$SANDBOX_DIR"
+    then
+        printf "%s: given sandbox $SANDBOX_DIR is invalid\n" "$(basename $0)" >&2
+        exit 1 
+    fi
+
+    ## Make any directories that don't already exist, this is OK to do here
+    ##  because we have already checked if it valid.
     export SANDBOX_DIR
     mkdir -p "$SANDBOX_DIR/upperdir" "$SANDBOX_DIR/workdir" "$SANDBOX_DIR/temproot"
 
@@ -32,7 +49,7 @@ try() {
     do
         ## Only make the directory if the original is a directory too
         if [ -d "$top_dir" ]; then
-            mkdir "$SANDBOX_DIR"/upperdir/"$top_dir" "$SANDBOX_DIR"/workdir"/$top_dir" "$SANDBOX_DIR"/temproot/"$top_dir"
+            mkdir -p "$SANDBOX_DIR"/upperdir/"$top_dir" "$SANDBOX_DIR"/workdir"/$top_dir" "$SANDBOX_DIR"/temproot/"$top_dir"
         fi
     done
 
@@ -140,7 +157,7 @@ summary() {
         exit 2
     elif ! [ -d "$SANDBOX_DIR/upperdir" ]
     then
-        printf "%s: could not find directory $SANDBOX_DIR\n" "$(basename $0)" >&2
+        printf "%s: could not find directory $SANDBOX_DIR/upperdir\n" "$(basename $0)" >&2
         exit 1
     fi
     
@@ -178,6 +195,16 @@ EOF
 ################################################################################
 
 commit() {
+    if ! [ -d "$SANDBOX_DIR" ]
+    then
+        printf "%s: could not find directory $SANDBOX_DIR\n" "$(basename $0)" >&2
+        exit 2
+    elif ! [ -d "$SANDBOX_DIR/upperdir" ]
+    then
+        printf "%s: could not find directory $SANDBOX_DIR/upperdir\n" "$(basename $0)" >&2
+        exit 1
+    fi
+
     changed_files=$(find_upperdir_changes "$SANDBOX_DIR")
     summary_output=$(process_changes "$SANDBOX_DIR" "$changed_files")
 
@@ -263,6 +290,31 @@ $changed_files
 EOF
 }
 
+## Returns 0 if a sandbox is empty (fresh for use)
+## or if it already exists, and is well-formed 
+sandbox_valid_or_empty() {
+    sandbox_dir="$1"
+    if [ ! -d "$sandbox_dir/upperdir" ] && [ ! -d "$sandbox_dir/workdir" ] && [ ! -d "$sandbox_dir/temproot" ]
+    then
+        ## No sandbox directory exists so we can happily return
+        return 0
+    fi
+
+    ## The sandbox already exists so we now need to check if it is valid
+    ## Validity requirements:
+    ## - no file exists in the temproot tree, i.e., all directories are empty
+    ##
+    ## TODO: Make this validity assertion tighter
+    ## KK 2023-06-28 workdir seems to be non-empty after a single use, is that expected?
+    if [ ! -z "$(find "$sandbox_dir/temproot" -depth -not -type d)" ]
+    then
+        return 1
+    fi
+
+    return 0
+}
+
+
 
 ################################################################################
 # Argument parsing